Add infinite buffer to health check consumers

[GuptaManan100]

Description

This PR fixes the problem described in #17629. As pointed out in the issue, the problem is that the consumers aren't fast enough to ingest all the health check updates and that causes them to miss some of them.

To prevent this, this PR adds a new message queue which keeps track of messages with an infinite capacity (we'll OOM eventually), while continuing to support the same semantics from the client side. The message queue has been added in a higher level package so that it can shared across the codebase if the use case for it arrises in the future.

Related Issue(s)

• Fixes Bug Report: vtgate buffering times out even after receiving healthcheck from new primary #17629

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]

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[codecov]

Codecov Report

Attention: Patch coverage is 94.28571% with 4 lines in your changes missing coverage. Please review.

Project coverage is 67.67%. Comparing base (a6c2896) to head (86ff824).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/concurrency/message_queue.go	89.47%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17632      +/-   ##
==========================================
+ Coverage   67.64%   67.67%   +0.03%     
==========================================
  Files        1586     1587       +1     
  Lines      255629   255732     +103     
==========================================
+ Hits       172910   173078     +168     
+ Misses      82719    82654      -65     

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[deepthi]

This will block if channel is full, correct?

[deepthi]

Let us add a metric that exports the size of this queue.

[GuptaManan100]

Okay 👍

[deepthi]

you need to put this access and the other one behind a mutex, otherwise race test fails.

[deepthi]

No back ports of this PR, please. Instead we can do #17634 on old release branches.