Add `ignore_component_digest_mismatch` option to `sstable_open_config`
that logs a warning instead of throwing `malformed_sstable_exception`
on component digest mismatch. This is useful for recovering sstables
with corrupted non-vital components or working around bugs in digest
calculation.
Expose the option in scylla-sstable via the
`--ignore-component-digest-mismatch` flag for the upgrade operation.