Cherry-pick #8159 and #8243 to v1.72.x

[purnesh42H]

Original PRs: #8159 #8243

RELEASE NOTES:

• ringhash: implement gRFC A76

[codecov]

Codecov Report

Attention: Patch coverage is 97.46835% with 4 lines in your changes missing coverage. Please review.

Project coverage is 82.17%. Comparing base (79ca174) to head (fe4b92f).
Report is 1 commits behind head on v1.72.x.

Files with missing lines	Patch %	Lines
internal/testutils/xds/e2e/clientresources.go	75.00%	1 Missing and 1 partial ⚠️
xds/internal/balancer/ringhash/picker.go	96.42%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           v1.72.x    #8255      +/-   ##
===========================================
+ Coverage    82.07%   82.17%   +0.09%     
===========================================
  Files          410      412       +2     
  Lines        40236    40346     +110     
===========================================
+ Hits         33024    33153     +129     
+ Misses        5856     5842      -14     
+ Partials      1356     1351       -5     

Files with missing lines	Coverage Δ
internal/envconfig/envconfig.go	100.00% <ø> (ø)
internal/metadata/metadata.go	82.08% <100.00%> (+1.44%)	⬆️
internal/testutils/envconfig.go	100.00% <100.00%> (ø)
resolver/ringhash/attr.go	100.00% <100.00%> (ø)
...internal/balancer/clusterresolver/configbuilder.go	91.22% <100.00%> (+0.05%)	⬆️
xds/internal/balancer/ringhash/config.go	92.30% <100.00%> (+3.41%)	⬆️
xds/internal/balancer/ringhash/ring.go	100.00% <100.00%> (+7.14%)	⬆️
xds/internal/balancer/ringhash/ringhash.go	94.22% <100.00%> (+0.35%)	⬆️
xds/internal/balancer/ringhash/util.go	100.00% <100.00%> (ø)
xds/internal/resolver/serviceconfig.go	85.71% <100.00%> (ø)
... and 3 more

... and 20 files with indirect coverage changes

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[arjan-bal]

Can you also cherrypick #8243 in the same PR?

Also mention the target branch name in the PR description.

[purnesh42H]

Can you also cherrypick #8243 in the same PR?

Also mention the target branch name in the PR description.

Done. I thought there will be conflict