Add a REST API to reload Raft topology state without having to restart a node and use it in `test_fence_hints`. Restarting the node has undesired side effects which cause test flakiness; more details provided in commit messages.
Refactor the test a bit while at it.
Fixes: #15285Closesscylladb/scylladb#15523
* github.com:scylladb/scylladb:
test: test_fencing.py: enable hints_manager=trace logs in `test_fence_hints`
test: test_fencing.py: reload topology through REST API in `test_fence_hints`
test: refactor test_fencing.py
api: storage_service: add REST API to reload topology state