fix: support minimum TLS v1.2 for webhook admission server

[shaneutt]

What this PR does / why we need it:

This is in direct response to the gosec lint which
we disabled due to backwards compatibility issues
in the v1.3.x releases of KIC, but now with KIC v2
on the horizon it's time to pull off the band-aid.

Which issue this PR fixes

Resolves #1065

PR Readiness Checklist:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Merging #1671 (38ff5bd) into next (b00580a) will decrease coverage by 0.47%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             next    #1671      +/-   ##
==========================================
- Coverage   46.23%   45.75%   -0.48%     
==========================================
  Files          70       70              
  Lines        6837     6838       +1     
==========================================
- Hits         3161     3129      -32     
- Misses       3304     3340      +36     
+ Partials      372      369       -3     

Flag	Coverage Δ
integration-test	45.75% <100.00%> (-0.48%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
internal/admission/server.go	30.76% <100.00%> (+0.41%)	⬆️
internal/sendconfig/sendconfig.go	41.48% <0.00%> (-12.60%)	⬇️
internal/ctrlutils/ingress-status.go	47.71% <0.00%> (-3.38%)	⬇️
internal/proxy/clientgo_cached_proxy_resolver.go	53.98% <0.00%> (-1.77%)	⬇️

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