Online DDL: unsupporting gh-ost DDL strategy

[shlomi-noach]

Description

See #15692

This PR:

• Removes the embedded gh-ost binary from vttablet (the user will have to supply their own gh-ost binary, and unless it's /usr/bin/gh-ost they will have to run vttablet --gh-ost-path)
• Removes onlineddl_ghost endtoend tests, and replaces gh-ost strategy tests with vitess strategy in any other tests.

With that, we turn gh-ost to be unsupported. Otherwise gh-ost strategy still works.

Related Issue(s)

• Tracking: deprecation of gh-ost and pt-osc Online DDL strategies #15692
• Documentation: 20.0 docs: unsupporting gh-ost website#1725

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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[shlomi-noach]

Docs PR: vitessio/website#1725

[dbussink]

Would it be worth to make this work if it's available in $PATH instead of having a hardcoded path? Would that already work out of the box if we just set these values to "gh-ost" and "pt-online-schema-change"?

Looking at the template below, that might already just work then?

[shlomi-noach]

Good point. Fixed.

[shlomi-noach]

pt-online-schema-change remains on /usr/bin as this was the previous behavior. Not changing it, will just remove it when the time comes.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 68.40%. Comparing base (6cd09cc) to head (48c9515).
Report is 6 commits behind head on main.

Files	Patch %	Lines
go/vt/vttablet/onlineddl/executor.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15693      +/-   ##
==========================================
+ Coverage   68.38%   68.40%   +0.02%     
==========================================
  Files        1556     1556              
  Lines      195120   195111       -9     
==========================================
+ Hits       133427   133466      +39     
+ Misses      61693    61645      -48     

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[mattlord]

LGTM! We need to update a couple of test output files now. I'll push a quick commit for that to save you the CI time when you're ready to merge.

[shlomi-noach]

@mattlord thank you!