[release-21.0] [Direct PR] Add RPC to read the reparent journal position

[GuptaManan100]

Description

This PR adds an RPC to read the reparent journal information. It is required for the PR #16926 to work well in release-22.0

Related Issue(s)

• Part of Bug Report: vtorc ERS incorrectly flags replica as having errant GTIDs #16724

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]

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

Attention: Patch coverage is 58.33333% with 20 lines in your changes missing coverage. Please review.

Project coverage is 69.41%. Comparing base (376c478) to head (2f26e6b).
Report is 2 commits behind head on release-21.0.

Files with missing lines	Patch %	Lines
go/vt/vttablet/tabletmanager/rpc_replication.go	0.00%	11 Missing ⚠️
go/vt/mysqlctl/reparent.go	0.00%	2 Missing ⚠️
go/vt/vtcombo/tablet_map.go	0.00%	2 Missing ⚠️
...t/vtctl/grpcvtctldserver/testutil/test_tmclient.go	0.00%	2 Missing ⚠️
go/vt/vttablet/faketmclient/fake_client.go	0.00%	2 Missing ⚠️
go/vt/vttablet/grpctmclient/client.go	88.88%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-21.0   #16982      +/-   ##
================================================
- Coverage         69.43%   69.41%   -0.03%     
================================================
  Files              1570     1570              
  Lines            203841   203889      +48     
================================================
- Hits             141547   141536      -11     
- Misses            62294    62353      +59     

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