Currently, repair_writer_impl::create_writer keeps erm to ensure that a sharder is valid. If we repair a tablet, erm blocks the state machine and no operation on any tablet of this table might be performed.
Use auto_refreshing_sharder and topology_guard to ensure that the operation is safe and that tablet operations on the whole table aren't blocked.
Fixes: #23453.
Needs backport to 2025.1 that introduces the tablet repair scheduler.
Closesscylladb/scylladb#23455
* github.com:scylladb/scylladb:
\test: add test to check concurrent migration and repair of two different tablets
repair: release erm in repair_writer_impl::create_writer when possible