### Summary
The fix turns a negative timeout into a finite 60 second wait inside
`MysqlDatabaseLock`, which both servers accept. Callers keep expressing
"block until available", and the equivalent PostgreSQL and GaussDB work
on the same `-1` semantics (#16346, #18506) is untouched. Non-negative
timeouts keep their current behaviour.
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Co-authored-by: Krim <git@krim.dev>
