Add List method to gRPC Health service

[marcoshuck]

This change introduces a new List RPC endpoint for the Health service, allowing clients to retrieve the statuses of all monitored services. This feature simplifies integration with status-reporting dashboards and enhances observability for microservices.

Proposal: grpc/proposal#468
gRPC-proto change: grpc/grpc-proto#143

[marcoshuck]

I regenerated the Go stubs using the work in progress version of grpc/grpc-proto#143

[marcoshuck]

I regenerated the Go stubs using the work in progress version of grpc/grpc-proto#143

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.17%. Comparing base (5668c66) to head (23a4f3a).
Report is 12 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8155      +/-   ##
==========================================
- Coverage   82.32%   82.17%   -0.16%     
==========================================
  Files         392      393       +1     
  Lines       39140    39159      +19     
==========================================
- Hits        32222    32177      -45     
- Misses       5597     5648      +51     
- Partials     1321     1334      +13     

Files with missing lines	Coverage Δ
health/server.go	95.83% <100.00%> (+0.83%)	⬆️

... and 36 files with indirect coverage changes

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[purnesh42H]

@marcoshuck i think we need to wait for the proposal and proto change to be merged before this? I still see them in review

@dfawley cc

[github-actions]

This PR is labeled as requiring an update from the reporter, and no update has been received after 6 days. If no update is provided in the next 7 days, this issue will be automatically closed.