metrics(virtualHosts): add support for opt-in virtual host metrics stats

[psinghal20]

What type of PR is this?

What this PR does / why we need it:
This PR adds support for enabling virtual host metrics stats by adding the virtual cluster configuration.

There is an API change in the EnvoyProxy spec with the addition of EnableVirtualHostStats in the Telemetry.Metrics configuration.

I have added a unit test for translation and xdsIR generation.

Which issue(s) this PR fixes:

Fixes #1822

[codecov]

Codecov Report

Merging #1855 (60a9652) into main (a324513) will increase coverage by 0.01%.
The diff coverage is 67.44%.

@@            Coverage Diff             @@
##             main    #1855      +/-   ##
==========================================
+ Coverage   65.24%   65.25%   +0.01%     
==========================================
  Files          86       86              
  Lines       12480    12520      +40     
==========================================
+ Hits         8142     8170      +28     
- Misses       3821     3832      +11     
- Partials      517      518       +1     

Files Changed	Coverage Δ
internal/ir/xds.go	73.60% <ø> (ø)
internal/ir/zz_generated.deepcopy.go	13.54% <0.00%> (-0.25%)	⬇️
internal/gatewayapi/listener.go	91.62% <100.00%> (+0.39%)	⬆️
internal/xds/translator/translator.go	79.85% <100.00%> (+1.36%)	⬆️

... and 2 files with indirect coverage changes

[arkodg]

Looks great, thanks @psinghal20 !