rpc: retrieve unresolved transactions

[harshit-gangal]

Description

This PR adds a new vttablet rpc to retrieve unresolved distributed transactions from the primary tablet.

Related Issue(s)

• RFC: Atomic Distributed Transactions #16245

Checklist

• 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

[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

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• 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 75.22124% with 28 lines in your changes missing coverage. Please review.

Project coverage is 68.70%. Comparing base (ff3425f) to head (36afb78).
Report is 3 commits behind head on main.

Files	Patch %	Lines
go/vt/vttablet/tabletserver/tabletserver.go	0.00%	11 Missing ⚠️
go/vt/vttablet/queryservice/wrapped.go	0.00%	7 Missing ⚠️
go/vt/vtcombo/tablet_map.go	0.00%	3 Missing ⚠️
go/vt/vttablet/sandboxconn/sandboxconn.go	0.00%	2 Missing ⚠️
go/vt/vttablet/tabletserver/dt_executor.go	0.00%	2 Missing ⚠️
go/vt/vttablet/tabletserver/twopc.go	94.11%	2 Missing ⚠️
go/vt/vttablet/grpctabletconn/conn.go	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16356      +/-   ##
==========================================
- Coverage   68.71%   68.70%   -0.01%     
==========================================
  Files        1547     1548       +1     
  Lines      198291   198567     +276     
==========================================
+ Hits       136256   136435     +179     
- Misses      62035    62132      +97     

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[GuptaManan100]

LGTM!