### 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
final IndexNameExpressionResolver indexNameExpressionResolver,
        final Client client,
        final RestoreService restoreService,
        final CcrLicenseChecker ccrLicenseChecker
    ) {
        super(
            PutFollowAction.NAME,
            transportService,
            clusterService,
            threadPool,
            actionFilters,
            PutFollowAction.Request::new,
            indexNameExpressionResolver,
            PutFollowAction.Response::new,
            EsExecutors.DIRECT_EXECUTOR_SERVICE
        );
        this.indexScopedSettings = indexScopedSettings;
        this.client = client;
        this.remoteClientResponseExecutor = threadPool.executor(CCR_THREAD_POOL_NAME);
        this.restoreService = restoreService;
        this.ccrLicenseChecker = Objects.requireNonNull(ccrLicenseChecker);
    }
    @Override
    protected void masterOperation(
        Task task,
        final PutFollowAction.Request request,
        final ClusterState state,
        final ActionListener<PutFollowAction.Response> listener
    ) {
        if (ccrLicenseChecker.isCcrAllowed() == false) {