CASSANDRA-21012: Allow CQLSSTableWriter to specify SSTable id type (legacy/uuid)

[arvindKandpal-ksolves]

Problem

CQLSSTableWriter always generates SSTables with legacy sequential identifiers. If someone writes SSTables standalone and loads them into a node with uuid_sstable_identifiers_enabled: true (via nodetool refresh), the legacy naming causes a mismatch since it's not converted to UUID format.

Fix

Added withUUIDSSTableIdentifiers(boolean) to CQLSSTableWriter.Builder, letting users explicitly choose legacy or UUID identifiers at build time.Default behavior (unset) falls back to the existing config-flag based logic — fully backward compatible.

Changes

• SSTableIdFactory: new builderFor(boolean) method
• AbstractSSTableSimpleWriter: instance-level idBuilder (static id counter
  kept as-is for cross-instance uniqueness)
• SSTableSimpleWriter / SSTableSimpleUnsortedWriter: new constructor overloads
• CQLSSTableWriter.Builder: new withUUIDSSTableIdentifiers(boolean) method

Testing

• Added unit tests for UUID mode and default (legacy) mode
• All existing tests pass (CQLSSTableWriterDaemonTest, CQLSSTableWriterClientTest)
• Manually verified end-to-end: wrote SSTables with UUID ids, copied into a live node with uuid_sstable_identifiers_enabled: true, ran nodetool refresh, confirmed data loaded correctly
• Verified both sorted and unsorted writer paths
• ant checkstyle passes

The Cassandra Jira

[smiklosovic]

I think this is better https://github.com/arvindKandpal-ksolves/cassandra/compare/CASSANDRA-21012...smiklosovic:cassandra:CASSANDRA-21012?expand=1

[smiklosovic]

https://github.com/arvindKandpal-ksolves/cassandra/compare/CASSANDRA-21012...smiklosovic:cassandra:CASSANDRA-21012?expand=1

[arvindKandpal-ksolves]

Thanks for the review, @smiklosovic! Applied the suggested changes.