fix(libsinsp): solve field-field comparison pointer instability issues

[jasondellaluce]

What type of PR is this?

/kind bug

Any specific area of the project related to this PR?

/area libsinsp

Does this PR require a change in the driver versions?

What this PR does / why we need it:

Internal tests demonstrated that field-to-field comparisons and/or filter caching can't just be broken with plugin fields (for which we enforced a STORAGE transformer layer in the compiler), but also with other fields were pointer stability between subsequent extractions on the same events (even on different fields) is not guaranteed.

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

fix(libsinsp): solve field-field comparison pointer instability issues 

[github-actions]

Perf diff from master - unit tests

     5.65%     +1.85%  [.] sinsp::next
     2.15%     -0.89%  [.] std::_Hashtable<long, std::pair<long const, std::shared_ptr<sinsp_threadinfo> >, std::allocator<std::pair<long const, std::shared_ptr<sinsp_threadinfo> > >, std::__detail::_Select1st, std::equal_to<long>, std::hash<long>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, false, true> >::_M_find_before_node
     5.00%     -0.84%  [.] sinsp_evt::load_params
     2.91%     -0.76%  [.] scap_event_decode_params
     5.56%     -0.71%  [.] next
     1.50%     -0.69%  [.] std::vector<sinsp_evt_param, std::allocator<sinsp_evt_param> >::emplace_back<sinsp_evt*, unsigned int&, char const*, unsigned long&>
     1.34%     +0.45%  [.] sinsp_parser::event_cleanup
     0.79%     +0.44%  [.] sinsp_filter_check::parse_field_name
     1.46%     -0.40%  [.] libsinsp::events::is_unknown_event
     0.81%     -0.40%  [.] sinsp_fdtable::find

Heap diff from master - unit tests

peak heap memory consumption: -419B
peak RSS (including heaptrack overhead): 0B
total memory leaked: 0B

Heap diff from master - scap file

peak heap memory consumption: 0B
peak RSS (including heaptrack overhead): 0B
total memory leaked: 0B

Benchmarks diff from master

Comparing gbench_data.json to /root/actions-runner/_work/libs/libs/build/gbench_data.json
Benchmark                                                         Time             CPU      Time Old      Time New       CPU Old       CPU New
----------------------------------------------------------------------------------------------------------------------------------------------
BM_sinsp_split_mean                                            +0.0066         +0.0066           149           150           149           150
BM_sinsp_split_median                                          +0.0079         +0.0079           149           150           149           150
BM_sinsp_split_stddev                                          -0.1837         -0.1851             1             1             1             1
BM_sinsp_split_cv                                              -0.1890         -0.1905             0             0             0             0
BM_sinsp_concatenate_paths_relative_path_mean                  -0.0929         -0.0929            47            42            47            42
BM_sinsp_concatenate_paths_relative_path_median                -0.0913         -0.0913            46            42            46            42
BM_sinsp_concatenate_paths_relative_path_stddev                -0.6232         -0.6243             0             0             0             0
BM_sinsp_concatenate_paths_relative_path_cv                    -0.5846         -0.5858             0             0             0             0
BM_sinsp_concatenate_paths_empty_path_mean                     -0.0063         -0.0063            17            17            17            17
BM_sinsp_concatenate_paths_empty_path_median                   -0.0019         -0.0019            17            17            17            17
BM_sinsp_concatenate_paths_empty_path_stddev                   -0.4590         -0.4588             0             0             0             0
BM_sinsp_concatenate_paths_empty_path_cv                       -0.4556         -0.4554             0             0             0             0
BM_sinsp_concatenate_paths_absolute_path_mean                  -0.1035         -0.1035            50            45            50            45
BM_sinsp_concatenate_paths_absolute_path_median                -0.1012         -0.1011            50            45            50            45
BM_sinsp_concatenate_paths_absolute_path_stddev                -0.6171         -0.6169             0             0             0             0
BM_sinsp_concatenate_paths_absolute_path_cv                    -0.5729         -0.5726             0             0             0             0
BM_sinsp_split_container_image_mean                            -0.0055         -0.0055           353           351           353           351
BM_sinsp_split_container_image_median                          +0.0009         +0.0009           350           351           350           351
BM_sinsp_split_container_image_stddev                          -0.5791         -0.5787             4             2             4             2
BM_sinsp_split_container_image_cv                              -0.5768         -0.5763             0             0             0             0

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.58%. Comparing base (5b9db23) to head (f851ffb).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2063      +/-   ##
==========================================
+ Coverage   73.55%   73.58%   +0.02%     
==========================================
  Files         253      253              
  Lines       31863    31867       +4     
  Branches     5651     5656       +5     
==========================================
+ Hits        23438    23450      +12     
+ Misses       8420     8417       -3     
+ Partials        5        0       -5     

Flag	Coverage Δ
libsinsp	73.58% <100.00%> (+0.02%)	⬆️

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[FedeDP]

/milestone 0.18.0

[FedeDP]

/approve

[poiana]

LGTM label has been added.

Git tree hash: c626582e698d97a96047ae1299d8a602e1736f97

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: FedeDP, jasondellaluce

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