fix(sql): restore advisory lock manager state on read-committed statement retry

[waterWang]

Fixes: #173169

The read-committed per-statement retry loop in dispatchReadCommittedStmtToExecutionEngine creates and rolls back its savepoint directly at the KV layer without notifying the advisory lock manager. The manager hooks are only wired into the SQL SAVEPOINT statements.

When a statement acquires a pg_advisory_xact_lock and then hits a retryable error in the same statement, KV correctly rolls back the lock but the manager's stack entry survives. If the retry does not re-acquire the same lock, pg_locks reports a granted advisory lock the session does not hold for the rest of the transaction.

This fix:

1. Captures a snapshot of the advisory lock manager state alongside the KV savepoint creation (using the existing ExportRewindSnapshot primitive).
2. Restores the snapshot after each read-committed statement retry rollback (using ApplyRewindSnapshot), keeping pg_locks consistent with KV.

The existing rewind primitives (ExportRewindSnapshot / ApplyRewindSnapshot in pkg/sql/advisorylock/manager.go) are reused as suggested in the issue. OnSQLRollbackToSavepoint cannot be used directly since the read-committed savepoint is not a SQL savepoint.

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• @spilchen (author of sql: stale advisory lock tracking after read-committed statement retry #173169)

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