Adds a `hinted_handoff_pause_hint_replay` error injection point. When
enabled, hint replay logic behaves as if it is run, but it gets stuck in
a loop and no hints are actually sent until the point is disabled again.
This injection point will be useful in dtests - it will simulate
infinitely slow hint replay and will make it possible to test how some
operations behave while hint replay logic is running.
The first intended use case of this injection point is testing the HTTP
API for waiting for hints (#8728).
Refs: #6649Closes#8801
* github.com:scylladb/scylla:
hints: fix indentation after previous patch
hints: error injection for pausing hint replay
hints: coroutinize lambda inside send_one_file