Fix TrimmedShardedDataChangeRecord to use AvroCoder everywhere in the template.

[aasthabharill]

b/459651641

Problem

We currently use SerializableCoder in Reverse Replication template which is quite slow and is contributing to the OOMs we've been seeing while running reverse jobs.

Fix

Fix TrimmedShardedDataChangeRecord to use AvroCoder everywhere in the template.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.24%. Comparing base (3c9a101) to head (09df198).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
...cloud/teleport/v2/templates/SpannerToSourceDb.java	0.00%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2993      +/-   ##
============================================
+ Coverage     50.19%   50.24%   +0.05%     
- Complexity     5000     5018      +18     
============================================
  Files           966      967       +1     
  Lines         59163    59260      +97     
  Branches       6449     6458       +9     
============================================
+ Hits          29695    29777      +82     
- Misses        27367    27377      +10     
- Partials       2101     2106       +5     

Components	Coverage Δ
spanner-templates	70.43% <0.00%> (-0.02%)	⬇️
spanner-import-export	68.96% <ø> (-0.04%)	⬇️
spanner-live-forward-migration	79.69% <ø> (ø)
spanner-live-reverse-replication	77.09% <0.00%> (+0.01%)	⬆️
spanner-bulk-migration	88.33% <ø> (ø)

Files with missing lines	Coverage Δ
...s/changestream/TrimmedShardedDataChangeRecord.java	83.60% <ø> (ø)
...cloud/teleport/v2/templates/SpannerToSourceDb.java	0.00% <0.00%> (ø)

... and 4 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[manitgupta]

Could you update the description with the Testing section detailing the tests that you have run?

[manitgupta]

I think you can close this PR for now since we need to do a round of functional and load testing before we can merge this.
The right owner can take up those items (along with the fix).