xds/rbac: add additional handling for addresses with ports

[mbissa]

This PR enhances the rbac matcher to handle IP address string with a port attached.

The fix introduces the net.SplitHostPort utility function, ensuring the port is properly stripped out of the underlying peerInfo.Addr.String() and localAddr.String() values before parsing them with netip.ParseAddr. A fallback mechanism is also included in case SplitHostPort fails due to a missing port.

RELEASE NOTES:

• xds/rbac: Add additional handling for addresses with ports

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.00%. Comparing base (b6597b3) to head (323fae8).
⚠️ Report is 23 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/xds/rbac/matchers.go	50.00%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8990      +/-   ##
==========================================
- Coverage   83.42%   83.00%   -0.42%     
==========================================
  Files         410      411       +1     
  Lines       32572    32902     +330     
==========================================
+ Hits        27172    27310     +138     
- Misses       4030     4191     +161     
- Partials     1370     1401      +31     

Files with missing lines	Coverage Δ
internal/xds/rbac/matchers.go	75.71% <50.00%> (-1.79%)	⬇️

... and 57 files with indirect coverage changes

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[arjan-bal]

How big of a change would it be to make match return a (bool, error) to enable callers to handle parsing errors?

[mbissa]

There are 11 implementations and each implementation has on an average of 4-5 references. This would need thorough testing and effort. I suggest we merge this and do that as a follow up.