Prepare schema tracking for all UDFs

[systay]

Description

We recently added support for UDFs to the schema tracker. This PR tweaks the gRPC APIs used to make them easier to grow with. We know we want to track types from UDFs in a not-too-distant future, so we might as well prepare the tracker and the gRPC apis to allow for that. This way we don't have the issue with mismatched versions between the vtgate and the vttablet when upgrading.

Related Issue(s)

First attempt: #15705
Planner changes: #15710

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

[vitess-bot]

Review Checklist

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[codecov]

Codecov Report

Attention: Patch coverage is 40.90909% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 68.41%. Comparing base (178e6e8) to head (b22d484).
Report is 3 commits behind head on main.

Files	Patch %	Lines
go/vt/vttablet/tabletserver/query_executor.go	0.00%	11 Missing ⚠️
go/vt/vtgate/schema/tracker.go	80.00%	1 Missing ⚠️
go/vt/vtgate/vtgate.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15732      +/-   ##
==========================================
+ Coverage   68.38%   68.41%   +0.02%     
==========================================
  Files        1556     1556              
  Lines      195361   195418      +57     
==========================================
+ Hits       133598   133695      +97     
+ Misses      61763    61723      -40     

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[harshit-gangal]

this looks unused.