GC: Support TiDB BR,Lightning,Dumpling use keyspace level GC when keyspace already enable it

## Enhancement
Support TiDB BR,Lightning,Dumpling use keyspace level GC when keyspace already enable it.
ref https://github.com/pingcap/tidb/pull/51300

## Implementation
If you want to import or export data from a keyspace, first get the keyspace meta from PD and check whether `gc_management_type` in meta is `keyspace_level_gc`. If it is `keyspace_level_gc` then use the PD client function `UpdateServiceSafePointV2` to update the service safe point.

Start by tracing the import and export paths for TiDB BR, Lightning, and Dumpling, then inspect how they obtain keyspace metadata from PD and where the PD client exposes UpdateServiceSafePointV2. Done means keyspace-level GC is detected from gc_management_type and the appropriate service safe point is updated for import and export operations.

Written by the indexing model from the issue text.