vttablet: add proxy support to FullStatus RPC in tabletmanager

[timvaillancourt]

Description

Add support for proxying FullStatus RPCs, in order for VTOrc to gain the ability to validate certain problems using many cells (locations) and detect network partitions - this will happen in future PRs (possibly v24), for now having this RPC in v24 will be helpful

Support for this is intentionally not added to vtctldclient GetFullStatus, because it's intended for internal VTOrc usage and I can't think of a good use case for someone at a CLI to need this

Related Issue(s)

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.

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

[codecov]

Codecov Report

❌ Patch coverage is 29.41176% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.87%. Comparing base (32b8bd8) to head (86c9825).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/vttablet/grpctmserver/server.go	29.03%	22 Missing ⚠️
go/vt/vtorc/inst/tablet_dao.go	0.00%	6 Missing ⚠️
go/vt/vttablet/tabletmanager/tm_init.go	0.00%	2 Missing ⚠️
go/vt/vttablet/tmrpctest/test_tm_rpc.go	50.00%	2 Missing ⚠️
go/vt/vtcombo/tablet_map.go	0.00%	1 Missing ⚠️
go/vt/vtorc/inst/instance_dao.go	0.00%	1 Missing ⚠️
go/vt/vttablet/faketmclient/fake_client.go	0.00%	1 Missing ⚠️
go/vt/wrangler/testlib/fake_tablet.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19058      +/-   ##
==========================================
- Coverage   69.89%   69.87%   -0.02%     
==========================================
  Files        1612     1613       +1     
  Lines      215826   216037     +211     
==========================================
+ Hits       150857   150962     +105     
- Misses      64969    65075     +106     

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