go/cmd/vtbackup: add --restore-from-clone support to vtbackup

[maxenglander]

Description

Next step after #19084. Add --restore-from-clone support to vtbackup. When --restore-from-clone is specified, vtbackup restores with MySQL CLONE rather than the last backup.

Related Issue(s)

• Feature Request: MySQL CLONE for vtbackup and vttablet restore #19061

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

AI Disclosure

[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.
• Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

• Bug fixes should have at least one unit or end-to-end test, enhancement and new features should have a sufficient number of tests.

Documentation

• Apply the release notes (needs details) label if users need to know about this change.
• New features should be documented.
• There should be some code comments as to why things are implemented the way they are.
• There should be a comment at the top of each new or modified test to explain what the test does.

New flags

• Is this flag really necessary?
• Flag names must be clear and intuitive, use dashes (-), and have a clear help text.

If a workflow is added or modified:

• Each item in Jobs should be named in order to mark it as required.
• If the workflow needs to be marked as required, the maintainer team must be notified.

Backward compatibility

• Protobuf changes should be wire-compatible.
• Changes to _vt tables and RPCs need to be backward compatible.
• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

❌ Patch coverage is 10.00000% with 36 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (clone-restore-init@cf1a804). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
go/cmd/vtbackup/cli/vtbackup.go	0.00%	36 Missing ⚠️

Additional details and impacted files

@@                  Coverage Diff                  @@
##             clone-restore-init   #19089   +/-   ##
=====================================================
  Coverage                      ?   69.88%           
=====================================================
  Files                         ?     1613           
  Lines                         ?   216120           
  Branches                      ?        0           
=====================================================
  Hits                          ?   151030           
  Misses                        ?    65090           
  Partials                      ?        0           

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