- remove some code that is obsolete in newer Scylla versions,
- fix some minor bugs. These bugs appear to be benign, there are no known issues caused by them, but fixing them is a good idea nevertheless,
- refactor some code for better maintainability.
Parts of this PR were extracted from https://github.com/scylladb/scylladb/pull/15331 (which was merged but later reverted), parts of it are new.
Closesscylladb/scylladb#16162
* github.com:scylladb/scylladb:
test/pylib: log_browsing: fix type hint
migration_manager: take `abort_source&` in get_schema_for_read/write
migration_manager: inline merge_schema_in_background
migration_manager: remove unused merge_schema_from overload
migration_manager: assume `canonical_mutation` support
migration_manager: add `std::move` to avoid a copy
schema_tables: refactor `scylla_tables(schema_features)`
schema_tables: pass `reload` flag when calling `merge_schema` cross-shard
system_keyspace: fix outdated comment
a472700309