feat(text-splitters): add MySQL Language support for RecursiveCharacterTextSplitter Class with delimiter aware splitting

[Emmanuel-Arokiaraj]

Description:
Enhanced RecursiveCharacterTextSplitter for Language.MYSQL by adding a comprehensive list of SQL separators including DDL, DML, and control-flow constructs. This enables more logical splitting of MySQL scripts—especially those containing stored procedures, triggers, functions, and multiline statements—while preserving structural integrity and block boundaries.

Additionally, improved delimiter handling so MySQL‐specific separators are evaluated before the default newline/space behavior, minimizing incorrect splits. Updated unit tests accordingly and adjusted chunk_size to avoid unintended recursive breaking during splitting.

Issue: N/A

Dependencies: None

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Test Notes

For the MySQL test test_mysql_query_splits, the previous configuration used chunk_size=100, but the first expected block exceeds 135 characters. With the default recursive behavior, this resulted in excessive splitting. Updated example usage:

splitter = RecursiveCharacterTextSplitter.from_language(
    language=Language.MYSQL,
    chunk_size=500,
    chunk_overlap=0,
)