### Elasticsearch Version

main

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

MacOS

### Problem Description

When there are 2 or more concurrent `_update` requests issued, one of them may fail with `ResourceAlreadyExistsException` exception which is misleading.


### Steps to Reproduce

1. Spawn a number of `_update` requests at the same time
2. Look at the results of these requests
3. Observe `ResourceAlreadyExistsException` being thrown in the case of conflict

### Logs (if relevant)

_No response_
x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/TransformMessages.java
public static final String REST_STOP_TRANSFORM_WAIT_FOR_COMPLETION_TIMEOUT =
        "Timed out after [{0}] while waiting for transform [{1}] to stop";
    public static final String REST_STOP_TRANSFORM_WAIT_FOR_COMPLETION_INTERRUPT = "Interrupted while waiting for transform [{0}] to stop";
    public static final String REST_PUT_TRANSFORM_EXISTS = "Transform with id [{0}] already exists";
    public static final String REST_UNKNOWN_TRANSFORM = "Transform with id [{0}] could not be found";
    public static final String REST_STOP_TRANSFORM_WITHOUT_CONFIG =
        "Detected transforms with no config [{0}]. Use force to stop/delete them.";
    public static final String REST_PUT_FAILED_PERSIST_TRANSFORM_CONFIGURATION = "Failed to persist transform configuration";
    public static final String REST_PUT_TRANSFORM_FAILED_TO_DEDUCE_DEST_MAPPINGS = "Failed to deduce dest mappings";
    public static final String REST_PUT_TRANSFORM_INCONSISTENT_ID =
        "Inconsistent id; ''{0}'' specified in the body differs from ''{1}'' specified as a URL argument";
    public static final String REST_FAILED_TO_SERIALIZE_TRANSFORM = "Failed to serialise transform [{0}]";
    public static final String TRANSFORM_FAILED_TO_PERSIST_STATS = "Failed to persist transform statistics for transform [{0}]";
    public static final String UNKNOWN_TRANSFORM_STATS = "Statistics for transform [{0}] could not be found";
    public static final String FAILED_TO_UNSET_RESET_MODE =
        "Failed to set [reset_mode] to [false] after {0}. To allow transforms to run, please call the feature reset API again";
    public static final String REST_WARN_NO_TRANSFORM_NODES =
        "Transform requires the transform node role for at least 1 node, found no transform nodes";
    public static final String CANNOT_STOP_FAILED_TRANSFORM = "Unable to stop transform [{0}] as it is in a failed state with reason [{1}]."
        + " Use force stop to stop the transform.";
    public static final String CANNOT_START_FAILED_TRANSFORM =
        "Unable to start transform [{0}] as it is in a failed state with failure: [{1}]. "
            + "Use force stop and then restart the transform once error is resolved.";