Remove deprecated usage of init_role() from API

[uranusjr]

Some cleanups found when investigating #18813.

init_role() has been replaced by bulk_update_roles(). This PR also slightly tweaked the ordering of operations so bulk_sync_roles() is only called when there's a need to update permissions, and added a few lines in the test to make sure role rename is performed successfully.

[github-actions]

The PR is likely OK to be merged with just subset of tests for default Python and Database versions without running the full matrix of tests, because it does not modify the core of Airflow. If the committers decide that the full tests matrix is needed, they will add the label 'full tests needed'. Then you should rebase to the latest main or amend the last commit of the PR, and push it with --force-with-lease.

[uranusjr]

I just realised instead of "name" not in data, this should check for emptiness and equality like the user endpoint.

[alex-astronomer]

Not sure how to request permission to add to this PR but will you please add this test to confirm that #18813 was fixed?

    def test_patch_updates_correct_roles_permissions(self):
        """
        Issue described in #18813, fixed by #18820
        """
        role_to_change = create_role(self.app, "patched_role")
        existing_role = create_role(self.app, "already_exists")
        assert len(role_to_change.permissions) == 0
        assert len(existing_role.permissions) == 0
        payload = {
            "name": "already_exists",
            "actions": [{"action": {"name": "can_delete"}, "resource": {"name": "XComs"}}],
        }
        response = self.client.patch(
            f"/api/v1/roles/{role_to_change.name}", json=payload, environ_overrides={"REMOTE_USER": "test"}
        )
        assert response.status_code == 200
        # have to use find_role because the session becomes detached during the test from the
        # previous role definitions
        assert len(self.app.appbuilder.sm.find_role("patched_role").permissions) == 1
        assert len(self.app.appbuilder.sm.find_role("already_exists").permissions) == 0
        expected_permission = role_to_change.permissions[0]
        assert (expected_permission.permission.name, expected_permission.view_menu.name) == (
            "can_delete",
            "XComs",
        )

This test fails on main but is corrected with #18820 (this PR)