Move write logic to OAP Server.

[wankai123]

Move the write logic to OAP Server, could have better control and set metrics for observing.

Part of related to apache/skywalking#13441

[Copilot]

Pull Request Overview

This PR migrates write logic from client-side bulk processors to direct OAP Server-side streaming, moving away from the bulk write pattern to enable better control and observability metrics on the server side.

Key changes:

• Removed client-side bulk write processors for traces, streams, and measures
• Updated test cases to use direct StreamObserver pattern instead of bulk processors
• Modified PropertyStore usage to instantiate directly rather than through client methods
• Made AbstractWrite.build() method public to support direct streaming

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
ITTraceTest.java	Replaced TraceBulkWriteProcessor with direct StreamObserver for trace writes
ITBanyanDBStreamQueryTests.java	Replaced StreamBulkWriteProcessor with direct StreamObserver for stream writes
ITBanyanDBPropertyTests.java	Changed property operations to use direct PropertyStore instantiation
ITBanyanDBMeasureQueryTests.java	Replaced MeasureBulkWriteProcessor with direct StreamObserver for measure writes
TraceBulkWriteProcessor.java	Removed entire bulk write processor implementation
StreamBulkWriteProcessor.java	Removed entire bulk write processor implementation
MeasureBulkWriteProcessor.java	Removed entire bulk write processor implementation
BanyanDBClient.java	Removed bulk processor factory methods and single write operations
AbstractWrite.java	Made build() method public and added getter for entityMetadata
AbstractBulkWriteProcessor.java	Removed entire abstract bulk write processor implementation

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