fix(mysql): handle spaced qualified identifiers

[Areson]

Why

MySQL digest text can add whitespace around dots in qualified identifiers. The lexer currently splits these names into separate tokens, preventing normalized SQL and table metadata from containing the complete identifier.

What

• Join whitespace-separated MySQL identifier components into a single qualified identifier
• Support quoted, partially quoted, keyword-named, Unicode, and wildcard components
• Preserve existing token behavior for unquoted calls and quoted identifiers
• Add regression coverage using a performance_schema digest-shaped query and long-identifier benchmarks

Risk Assessment

Low — the behavior is gated to MySQL and only changes qualified names containing whitespace around a dot. Other DBMS behavior and ordinary MySQL allocation costs remain unchanged.

Validation

• Go 1.25.7 unit tests, race detector, and vet
• Both fuzz targets for 60 seconds
• golangci-lint v2.9.0
• Targeted benchmarks confirm linear scaling and no ordinary-query allocation regression

References

• Fixes Normalized MySQL Queries Are Not Parsed Properly #80