[Improvement] Remove the JCasbin enforcer from the Gravitino authorizer

### What would you like to be improved?

After #12174 moves privilege policies from JCasbin `p` rules to a per-role policy index, the remaining enforcer only stores the user/group-to-role grouping graph.

This duplicates role membership already resolved from the version-validated user/group role caches. It also retains unnecessary shared mutable state, JCasbin model initialization, adapter code, resources, tests, and the JCasbin dependency in `server-common`.

### How should we improve?

Remove the enforcer from `JcasbinAuthorizer`:

- Compute the union of direct and group-inherited role IDs in `loadRolePrivilege`.
- Store the immutable effective role ID set in `AuthorizationRequestContext`.
- Resolve privilege effects and deny-policy checks against this request-scoped role set and the existing per-role `Map` index.
- Preserve global DENY precedence, active-role narrowing for ALLOW, OWNER handling, and role-version validation.
- Remove enforcer grouping-row binding and pruning.
- Remove the unused JCasbin adapter, model resources, model tests, and the JCasbin dependency from `server-common`.
- Add regression tests covering direct/group roles, role changes between requests, active roles, and DENY precedence.

The JCasbin dependency used independently by the Iceberg REST server is outside this change.

Related: #12173, #12174, #10908.

Start in server-common at JcasbinAuthorizer, loadRolePrivilege, and AuthorizationRequestContext; trace how direct and group-inherited roles and the existing per-role policy index are used. Review the enforcer adapter, model resources, model tests, and regression-test area before running the relevant authorization tests. Done means the enforcer and its dependency are removed from server-common while role-version validation, active-role narrowing, OWNER handling, and global DENY precedence remain covered.

Written by the indexing model from the issue text.