feat: allow TLS termination for TLSRoute

[NomadXD]

What type of PR is this?
Envoy Gateway API implementation doesn't support TLSRoute with TLS termination. Creating a TLSRoute that attaches to a TLS-terminating listener will be rejected by the implementation, which means that it is not conformant to the specification. This PR adds TLS termination support for TLSRoutes.

What this PR does / why we need it:
This PR implements the required changes for supporting TLS termination for TLSRoutes. This include TLS termination mode listener validation and TLSRoute translation.

Which issue(s) this PR fixes:

Fixes #6609

Release Notes: No

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.45%. Comparing base (0fa26d7) to head (5133d3d).
⚠️ Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7676      +/-   ##
==========================================
+ Coverage   72.43%   72.45%   +0.02%     
==========================================
  Files         232      232              
  Lines       34307    34307              
==========================================
+ Hits        24849    24857       +8     
+ Misses       7682     7676       -6     
+ Partials     1776     1774       -2     

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