feat: implement delete stream

[markwylde]

This PR introduces a new deleteStream method to the Eventbase instance, enabling complete cleanup of a stream and its associated resources. In addition, it removes an obsolete database creation function from src/db.ts, simplifying our codebase.

Key Changes:

1. Removed src/db.ts:

   • The createDb function (which handled creating or opening a doubledb instance) has been removed as it was no longer used in the project.

2. Updated src/index.ts:

   • Added a new deleteStream method to the Eventbase interface. This method:
     • Purges the JetStream stream via jsm.streams.purge.
     • Deletes the stream using jsm.streams.delete.
     • Closes the Eventbase instance.
     • Closes all underlying databases (db, metaDb, settingsDb).
     • Removes the filesystem directory (using rmdir) where the database files reside
   • Wrapped the stream stop sequence in a try-catch to gracefully handle potential errors.