Move the 'get_datetime_diff' function to 'wazuh-testing' utils module

[yanazaeva]

Related issue
#2287

Description

This closes #2287. The aim of this pull is to move the get_datetime_diff function from the cluster_performance_test into the wazuh_testing.utils module. After this change, the test continues to work as expected:

(wazuh_qa_env) yanazaeva@pop-os:~/git/wazuh-qa/deps/wazuh_testing$ python3.9 -m pytest  ../../tests/performance/test_cluster/test_cluster_performance/ --artifacts_path=/docs/rc5/50000A25W --n_workers=25 --n_agents=50000
=============================================================================================== test session starts ===============================================================================================
platform linux -- Python 3.9.5, pytest-6.2.2, py-1.10.0, pluggy-0.13.1
rootdir: /home/yanazaeva/git/wazuh-qa
plugins: testinfra-5.0.0, metadata-1.11.0, html-3.1.1
collected 1 item                                                                                                                                                                                                  

../../tests/performance/test_cluster/test_cluster_performance/test_cluster_performance.py .                                                                                                                 [100%]

================================================================================================ 1 passed in 0.50s ================================================================================================

	Results
R1	🟢
R2	🟢
R3	🟢

[juliamagan]

Why is this change needed in this PR?

[Selutario]

The current thresholds are too small and strict, which causes most tests to be considered failed. It will be necessary to increase them little by little so that they only fail if an environment really has unusually high resource consumption.

[Selutario]

PR update

I fixed the conflicts. These are the results of test_cluster_performance.py when using this artifacts:

python3 -m pytest tests/performance/test_cluster/test_cluster_performance/ --artifacts_path='/home/selu/Descargas/cluster_performance/107' --html=report.html --self-contained-html --n_workers=25 --n_agents=50000
============================================================================================ test session starts ============================================================================================
platform linux -- Python 3.8.10, pytest-5.0.0, py-1.8.2, pluggy-0.13.1
rootdir: /home/selu/Git/wazuh-qa
plugins: metadata-1.10.0, html-3.1.1, testinfra-5.0.0, tavern-1.2.2, pep8-1.0.6, cov-2.10.0, asyncio-0.14.0
collected 1 item                                                                                                                                                                                            

tests/performance/test_cluster/test_cluster_performance/test_cluster_performance.py .                                                                                                                 [100%]

---------------------------------------------------------------------- generated html file: file:///home/selu/Git/wazuh-qa/report.html ----------------------------------------------------------------------
=================================================================================== 1 passed, 2 warnings in 0.81 seconds ====================================================================================

[juliamagan]

24/05/2022

Testing

We have used the artifacts attached here

	Results
R1	🟢
R2	🟢
R3	🟢

[juliamagan]

LGTM