CASSANDRA-21115: Fix auto-repair skipping incomplete first repair after node restart

[pauloricardomg]

When a node crashes during its first auto-repair, the repair was incorrectly skipped by the "too soon" check after restart. This happened because tooSoonToRunRepair() uses repair_finish_ts which was set to the record creation time, not when repair actually finished. The in-progress detection logic in myTurnToRunRepair() was never reached.

The fix adds an in-progress check within tooSoonToRunRepair() that detects when repair_start_ts > repair_finish_ts and allows the repair to resume.

Patch by Paulo Motta; reviewed by X for CASSANDRA-21115

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