**Affected version:** 8.2 - 8.5.2
**Fixed in:** 8.5.3

### Problem Description

The problem applies to transforms that use more than 1 CCS cluster or 1 local and 1 CCS as source. A typical source could look like this (the important part: `remotes*`):

```
        "index" : [
          "remotes*:filebeat*"
        ],

```

If 2 indices share the same name the transform might fail with an error similar to this:

```
 Failed to retrieve checkpoint due to: Duplicate key logs-2022-11-14 (attempted merging values [... and ...]
```

Similar to the above the `_stats` call is broken for such a transform, it can fail with an error message starting with:

```
Failure during checkpoint retrieval
```

This can happen even if the transform is in state `STOPPED` or `FAILED`.

### Mitigation

Choose _one_ of the following mitigations:

 - split your transforms to use max 1 CCS/local indices

_or_

 - avoid upgrading to 8.2, until the issue got resolved (this is a regression of #80984)

_or_

 - avoid duplicate names for your indices even on remote cluster, e.g. name the index: `remote1-filebeat...`, `remote2-filebeat...`


### Solution

This is a regression of #80984 which introduced a new way of check-pointing. The remote needs to be prefixed to the index name.
x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/checkpoint/DefaultCheckpointProvider.java
private static final int AUDIT_CONCRETED_SOURCE_INDEX_CHANGES = 10;
    private static final Logger logger = LogManager.getLogger(DefaultCheckpointProvider.class);
    protected final Clock clock;
    protected final Client client;
    protected final RemoteClusterResolver remoteClusterResolver;
    protected final TransformConfigManager transformConfigManager;
    protected final TransformAuditor transformAuditor;
    protected final TransformConfig transformConfig;
    
    private final Set<String> fallbackToBWC = new HashSet<>();
    DefaultCheckpointProvider(
        final Clock clock,
        final Client client,
        final RemoteClusterResolver remoteClusterResolver,