[improve][broker] Migrate remaining broker proto files from protobuf to LightProto

[merlimat]

Summary

• Migrate SchemaStorageFormat, SchemaRegistryFormat, and DelayedMessageIndexBucketMetadata proto files to use LightProto generated code instead of standard protobuf
• Add the 3 proto files to lightproto-maven-plugin config and remove the protobuf compile goal (keeping only test-compile for test-only proto files)
• Replace Builder patterns, ByteString, and static parseFrom with LightProto's mutable API, byte[], and instance-based parseFrom

Test plan

• Verify mvn compile -pl pulsar-broker passes
• Verify mvn test-compile -pl pulsar-broker passes
• Run BookkeeperBucketSnapshotStorageTest
• Run SchemaTest
• Run schema-related integration tests

Documentation

• doc-required

  (Your PR needs to update docs and you will update later)

• doc-not-needed

  (Your PR doesn't need any doc update)

• doc

  (Your PR contains doc changes)

• doc-complete

  (Docs have been already added)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 91.21622% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.75%. Comparing base (be87cd9) to head (2909eba).
⚠️ Report is 42 commits behind head on master.

Files with missing lines	Patch %	Lines
...broker/service/schema/BookkeeperSchemaStorage.java	90.00%	7 Missing and 2 partials ⚠️
...oker/service/schema/SchemaRegistryServiceImpl.java	88.00%	1 Missing and 2 partials ⚠️
...g/apache/pulsar/PulsarClusterMetadataTeardown.java	83.33%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #25337       +/-   ##
=============================================
+ Coverage     37.37%   72.75%   +35.37%     
- Complexity    13188    33868    +20680     
=============================================
  Files          1897     1954       +57     
  Lines        150557   154762     +4205     
  Branches      17215    17721      +506     
=============================================
+ Hits          56276   112595    +56319     
+ Misses        86612    33135    -53477     
- Partials       7669     9032     +1363     

Flag	Coverage Δ
inttests	25.96% <62.83%> (+0.17%)	⬆️
systests	22.60% <60.13%> (+0.13%)	⬆️
unittests	73.73% <87.83%> (+39.58%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...elayed/bucket/BookkeeperBucketSnapshotStorage.java	82.81% <100.00%> (+82.81%)	⬆️
.../pulsar/broker/delayed/bucket/ImmutableBucket.java	85.58% <100.00%> (+85.58%)	⬆️
...he/pulsar/broker/delayed/bucket/MutableBucket.java	93.91% <100.00%> (+93.91%)	⬆️
...g/apache/pulsar/PulsarClusterMetadataTeardown.java	74.81% <83.33%> (+3.91%)	⬆️
...oker/service/schema/SchemaRegistryServiceImpl.java	81.04% <88.00%> (+17.75%)	⬆️
...broker/service/schema/BookkeeperSchemaStorage.java	78.14% <90.00%> (+9.46%)	⬆️

... and 1411 files with indirect coverage changes

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