[release-1.27] Enable TLSv1.2 for ZTunnel when in FIPS mode (#1596)

[zmiklank]

• Enable TLSv1.2 for ZTunnel when in FIPS mode

This change builds on istio/ztunnel#1711 which adds TLSv1.2 support to ZTunnel when TLS12_ENABLED is set to true. This patch will always set the env var when in FIPS mode, for all versions of ZTunnel, even though it is only supported from 1.29+, but the env var will simply be ignored by versions that don't support it.

• Make sure that FipsEnabled is restored to original value

In our tests, we sometimes set FipsEnabled manually. We should make sure to reset it to its original value during test cleanup.

Cherry-pick of #1547

[istio-testing]

Hi @zmiklank. Thanks for your PR.

I'm waiting for a istio-ecosystem or istio member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.38%. Comparing base (2c88e1d) to head (e4cde64).
⚠️ Report is 1 commits behind head on release-1.27.

Files with missing lines	Patch %	Lines
controllers/ztunnel/ztunnel_controller.go	33.33%	1 Missing and 1 partial ⚠️
pkg/istiovalues/fips.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.27    #1606      +/-   ##
================================================
+ Coverage         80.35%   80.38%   +0.02%     
================================================
  Files                44       44              
  Lines              2291     2299       +8     
================================================
+ Hits               1841     1848       +7     
  Misses              330      330              
- Partials            120      121       +1     

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[sridhargaddam]

/ok-to-test

[sridhargaddam]

LGTM, thanks.