Remove Dead Legacy Workflow Manager Code

[mattlord]

Description

The legacy sharding code was removed in v15, but this old workflow management code is even older than the legacy sharding code. It did not work and was dead code, so is being removed here in v16.

Related Issue(s)

• [Docs Review] Workflows website#1284

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests not required
• Documentation: Deletes dead docs content for dead workflows mgmt code website#1348

[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.
• If this is a change that users need to know about, please apply the release notes (needs details) label so that merging is blocked unless the summary release notes document is included.
• If a test is added or modified, there should be a documentation on top of the test to explain what the expected behavior is what the test does.

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• Is it really necessary to add this flag?
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If a workflow is added or modified:

• Each item in Jobs should be named in order to mark it as required.
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Bug fixes

• There should be at least one unit or end-to-end test.
• The Pull Request description should include a link to an issue that describes the bug.

Non-trivial changes

• There should be some code comments as to why things are implemented the way they are.

New/Existing features

• Should be documented, either by modifying the existing documentation or creating new documentation.
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Backward compatibility

• Protobuf changes should be wire-compatible.
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• vtctl command output order should be stable and awk-able.
• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from VTop, if used there.

[ajm188]

lgtm!

[GuptaManan100]

Folks, we missed the part that when we delete flags, we've to check if VTop is also using them. If it is, then we delete the usage there too. That's the last item in backward compatibility subsection of checklist.
I traced this from the failure in planetscale/vitess-operator#359

[GuptaManan100]

Here is the fix for VTop - planetscale/vitess-operator#360

[GuptaManan100]

This PR fixes release-15.0 too, so that upgrade-downgrade tests start working again - #12128