Added a new parameter `consider_only_existing_data` to major compaction
API endpoints. When enabled, major compaction will:
- Force-flush all tables.
- Force a new active segment in the commit log.
- Compact all existing SSTables and garbage-collect tombstones by only
checking the SSTables being compacted. Memtables, commit logs, and
other SSTables not part of the compaction will not be checked, as they
will only contain newer data that arrived after the compaction
started.
The `consider_only_existing_data` is passed down to the compaction
descriptor's `gc_check_only_compacting_sstables` option to ensure that
only the existing data is considered for garbage collection.
The option is also passed to the `maybe_flush_commitlog` method to make
sure all the tables are flushed and a new active segment is created in
the commit log.
Fixes#19728
Signed-off-by: Lakshmi Narayanan Sreethar <lakshmi.sreethar@scylladb.com>