xds: fix ipFamily always nil

[juwon8891]

chore: fix ipFamily always nil

What this PR does / why we need it:
This PR improves IP family configuration handling across different listener types and updates the DNS lookup strategy for better dual-stack support.

• Add consistent IP family handling across all listener types

Which issue(s) this PR fixes:
Fixes #4761

[codecov]

Codecov Report

Attention: Patch coverage is 62.50000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 65.62%. Comparing base (a383dd9) to head (64f4832).

Files with missing lines	Patch %	Lines
internal/gatewayapi/helpers.go	0.00%	3 Missing ⚠️
internal/xds/translator/cluster.go	50.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4782   +/-   ##
=======================================
  Coverage   65.61%   65.62%           
=======================================
  Files         211      211           
  Lines       31989    31997    +8     
=======================================
+ Hits        20991    20999    +8     
+ Misses       9760     9759    -1     
- Partials     1238     1239    +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[arkodg]

this is incorrect, you are using the listener level IPFamily value in the cluster
you should be deriving this value using a new IPFamily field in
https://github.com/envoyproxy/gateway/blame/48a0310082ceeaf4d3af17e6b6844c7d0fb5db0b/internal/ir/xds.go#L1297 instead and this should be set in the gateway api layer using the Backend Service / EndpointSlice info

[juwon8891]

Thanks for the feedback! I’ve updated the code to use a new IPFamily field
cc @zirain