Spring-ai Move batching strategy to base vector store builder

Moving BatchingStrategy configuration from individual vector store implementations to the base AbstractVectorStoreBuilder to reduce code duplication and provide consistent batching behavior across all vector stores.

The default TokenCountBatchingStrategy is now set in the base builder class.

Comment From: ilayaperumalg

LGTM, merging.

Comment From: ilayaperumalg

Rebased, fixed the conflicts and merged as 9844a1898