Fail VTBackup early when replication or MySQL is failing

[frouioui]

Description

As described in #17355 and #17043, vtbackup "ignores" replication failures and fatal mysql error. Leading to vtbackup processes undesirably running for longer than needed, or worse, stalling.

This Pull Request brings two new enhancements to vtbackup to solve both issues:

• When the mysqld instance created by vtbackup fails, vtbackup will now be aware of it (thanks to mysqld.OnFailure()) and will cancel its context which will make the process exit faster.
• The vtbackup process is now limiting the number of sequential replication errors it had to avoid waiting forever when replication is not working. If there are only transient errors, the process will not fail. Unless it reaches the limit of sequential errors, which I have set to 60 for now. As we try to get the replication status every second, this means we will be allowing a minimum of 60 seconds of sequential errors before failing.

Related Issue(s)

• Fix VTBackup continues working even if MySQL exited unexpectedly #17355
• Fix Fail VTBackup early when MySQL fails to start replication #17043

[vitess-bot]

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 21 lines in your changes missing coverage. Please review.

Project coverage is 67.69%. Comparing base (4370a48) to head (5f21d18).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
go/cmd/vtbackup/cli/vtbackup.go	0.00%	21 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17356      +/-   ##
==========================================
- Coverage   67.69%   67.69%   -0.01%     
==========================================
  Files        1585     1585              
  Lines      254904   254918      +14     
==========================================
+ Hits       172565   172574       +9     
- Misses      82339    82344       +5     

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[github-actions]

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[shlomi-noach]

Use LastError as Matt suggested elsewhere.

[mattlord]

Nice and simple and clean, I love it! ❤️