Implement endpoints needed for Permissions revamp

[pavish]

Items below are arranged in order of implementation. This order might change during the course of implementation.

### Home page
- [ ] https://github.com/mathesar-foundation/mathesar/issues/3654
- [ ] https://github.com/mathesar-foundation/mathesar/issues/3655
- [ ] https://github.com/mathesar-foundation/mathesar/issues/3656

### Databases page
- [ ] databases.get
- [ ] https://github.com/mathesar-foundation/mathesar/issues/3659
- [ ] https://github.com/mathesar-foundation/mathesar/issues/3660
- [ ] https://github.com/mathesar-foundation/mathesar/issues/3661
- [ ] https://github.com/mathesar-foundation/mathesar/issues/3657
- [ ] https://github.com/mathesar-foundation/mathesar/issues/3658
- [ ] collaborators.delete
- [ ] collaborators.modify_role_for_user
- [ ] https://github.com/mathesar-foundation/mathesar/issues/3662
- [ ] databases.privileges.grant
- [ ] databases.privileges.revoke
- [ ] databases.privileges.transfer_ownership
- [ ] roles.add: `(database_id, role_name, password) => RoleInfo`
- [ ] roles.delete: `(database_id, role_oid) => void`
- [ ] roles.add_members: `(database_id, role_oid, members: role_oids[]) => RoleInfo`
- [ ] roles.remove_members: `(database_id, role_oid, members: role_oids[]) => RoleInfo`
- [ ] schemas.list: should include privilege information for all roles
- [ ] schemas.add: should require owning role
- [ ] roles.grant_admin_option_to_member: `(database_id, role_oid, member_role_oid) => RoleInfo`
- [ ] roles.revoke_admin_option_to_member: `(database_id, role_oid, member_role_oid) => RoleInfo`
- [ ] databases.disconnect
- [ ] databases.list_databases_in_server
- [ ] databases.drop
- [ ] databases.privileges.list_owned_objects_recursively
- [ ] databases.privileges.transfer_ownership_recursively

### Schemas page
- [ ] schemas.get: should include privilege information for all roles
- [ ] schemas.privileges.grant
- [ ] schemas.privileges.revoke
- [ ] schemas.privileges.transfer_ownership
- [ ] tables.list: should include privilege information for all roles
- [ ] tables.add: should require owning role
- [ ] schemas.privileges.list_owned_objects_recursively
- [ ] schemas.privileges.transfer_ownership_recursively

### Tables page
- [ ] tables.get: should include privilege information for all roles
- [ ] tables.privileges.grant
- [ ] tables.privileges.revoke
- [ ] tables.privileges.transfer_ownership

### Users
- [ ] Add accent colors and avatar initials to users