### Description

It is impossible to create a follower index with a `$` character in its name (please note, it is possible to create a regular index with `$` in its name).

This could be reproduced by rest request:
```
PUT /my-index/_ccr/follow
{
    "remote_cluster": "my-remote-cluster",
    "leader_index": "my-index$follower"
}
```

or `CcrIntegTestCase`:

```
    public void testFollowIndex() throws Exception {
        assertAcked(leaderClient().admin().indices().prepareCreate("my$index"));
        setupRemoteCluster();
        final PutFollowAction.Request followRequest = putFollow("my$index", "my$index");
        followerClient().execute(PutFollowAction.INSTANCE, followRequest).get();
    }
```

This is happening as during initial follow phase we restore the leader cluster from the remote using a snapshot restore.
Corresponding request is created with index name added to `RestoreSnapshotRequest#renamePattern` (regexp) without escaping `$`.

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/action/TransportPutFollowAction.java
private static final Logger logger = LogManager.getLogger(TransportPutFollowAction.class);
    private final IndexScopedSettings indexScopedSettings;
    private final Client client;
    private final Executor remoteClientResponseExecutor;
    private final RestoreService restoreService;
    private final CcrLicenseChecker ccrLicenseChecker;
    @Inject
    public TransportPutFollowAction(
        final ThreadPool threadPool,
        final TransportService transportService,
        final ClusterService clusterService,
        final IndexScopedSettings indexScopedSettings,
        final ActionFilters actionFilters,