**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/test/java/org/elasticsearch/xpack/transform/checkpoint/DefaultCheckpointProviderTests.java
org.elasticsearch.xpack.core.common.notifications.Level.INFO,
                transformId,
                "Source index resolve found changes, removedIndexes: [index], new indexes: []"
            ),
            () -> { provider.reportSourceIndexChanges(Sets.newHashSet("index", "other_index"), Collections.singleton("other_index")); }
        );
        assertExpectation(
            new MockLogAppender.SeenEventExpectation(
                "info about adds/removal",
                checkpointProviderLogger.getName(),
                Level.DEBUG,
                "[" + transformId + "] Source index resolve found changes, removedIndexes: [], new indexes: [other_index]"
            ),
            new MockTransformAuditor.SeenAuditExpectation(
                "info about adds/removal",
                org.elasticsearch.xpack.core.common.notifications.Level.INFO,
                transformId,
                "Source index resolve found changes, removedIndexes: [], new indexes: [other_index]"
            ),
            () -> { provider.reportSourceIndexChanges(Collections.singleton("index"), Sets.newHashSet("index", "other_index")); }
        );
    }
    public void testReportSourceIndexChangesAddDeleteMany() throws Exception {
        String transformId = getTestName();
        TransformConfig transformConfig = TransformConfigTests.randomTransformConfig(transformId);
        DefaultCheckpointProvider provider = newCheckpointProvider(transformConfig);
        HashSet<String> oldSet = new HashSet<>();
        for (int i = 0; i < 100; ++i) {
            oldSet.add(String.valueOf(i));
        }