[release-20.0] Support passing filters to discovery.NewHealthCheck(…) (#16170)

[timvaillancourt]

Description

This PR is a manual backport of #16170 to release-20.0 (as discussed offline with @deepthi)

The reasoning for this backport is it resolves a regression in the txthrottler (in vttablet) that causes a healthcheck stream to be opened to N x tablets (every tablet in every cell), when only the local shard tablets are required. This regression began in v15 when go/vt/discovery was refactored

Related Issue(s)

#16170

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• Ensure that the Pull Request has a descriptive title.
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[codecov]

Codecov Report

Attention: Patch coverage is 63.82979% with 17 lines in your changes missing coverage. Please review.

Project coverage is 68.67%. Comparing base (4e82d72) to head (9dd3456).
Report is 1 commits behind head on release-20.0.

Files with missing lines	Patch %	Lines
.../vttablet/tabletserver/txthrottler/tx_throttler.go	57.14%	12 Missing ⚠️
go/vt/vtgate/tabletgateway.go	0.00%	4 Missing ⚠️
go/vt/throttler/demo/throttler_demo.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-20.0   #16872      +/-   ##
================================================
+ Coverage         68.65%   68.67%   +0.01%     
================================================
  Files              1541     1541              
  Lines            197937   197951      +14     
================================================
+ Hits             135903   135940      +37     
+ Misses            62034    62011      -23     

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