[KYUUBI #6901] Default policy for spark

### Why are the changes needed?
Added a service definition for spark which in turn enables the creation of a default policy for the spark service.
Default policy will block access until another policy is downloaded from Apache Ranger.

### How was this patch tested?
Tested manually.
Configure Kyuubi Authz plugin. Do not start Apache Ranger, it must not be reachable.
Make sure that policy cache is empty.
Start Kyuubi engine and try to query any tables. The default policy should not allow any access.
Previously the access was not restricted because there wasn't a default policy defined.

### Was this patch authored or co-authored using generative AI tooling?
No.

Closes #6902 from developster/master.

Closes #6901

feb6ebf [Octavian Ciubotaru] Default policy for spark

Authored-by: Octavian Ciubotaru <[email protected]>
Signed-off-by: Kent Yao <[email protected]>

Author: developster