[BUG] The create detector flow with cross-cluster indices is not working in the MDS app

[jackiehanyang]

What is the bug?
The create detector flow with cross-cluster indices is not working in the MDS app. After selecting cross-cluster on the create detector page, the timestamp dropdown does not populate with any options, blocking the creation flow.

What needs to be fixed

• When selecting remote indices, make sure the Timestamp field is populated with the correct options.
• when clean up Clusters dropdown list, also clean up Index and Timestamp field

[kaituo]

@amitgalitz Can you please take a look?