go/vt/{mysqlctl,vttablet}: support restore tablet with CLONE

[maxenglander]

Description

Next step after #19064. Adapted from @nickvanw code in private fork.

• Add support to VTTablet for --restore-with-clone.
• --restore-with-clone uses tabletmanager.restoreFromClone().
• restoreFromClone() and RestoreBackup() use shared functions extracted from RestoreBackup.

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

AI was used.

[vitess-bot]

Review Checklist

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• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

❌ Patch coverage is 8.28402% with 155 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.89%. Comparing base (d40490b) to head (cf1a804).

Files with missing lines	Patch %	Lines
go/vt/vttablet/tabletmanager/restore.go	1.41%	139 Missing ⚠️
go/vt/vttablet/tabletmanager/tm_init.go	26.31%	14 Missing ⚠️
go/vt/mysqlctl/backup.go	85.71%	1 Missing ⚠️
go/vt/vttablet/tabletmanager/rpc_backup.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                  @@
##           clone-from-donor   #19084      +/-   ##
====================================================
- Coverage             69.91%   69.89%   -0.03%     
====================================================
  Files                  1613     1613              
  Lines                216020   216111      +91     
====================================================
+ Hits                 151031   151050      +19     
- Misses                64989    65061      +72     

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[maxenglander]

these changes allow this to be called from both tabletmanager.restoreFromClone() and tabletmanager.RestoreBackup() without the former needing to construct RestoreParams, which is otherwise not needed by restoreFromClone().