[ML] addresses preview bug, and adds check to PUT (#41803)

[benwtrent]

Bug fixes:

• NPE error on _preview if source index does not exists
• NPE error on put if destination index exists and security is enabled

Additionally checks for the following dest.index and source.index are done:

• That any of the source index names match (simple regex) the dest.index
• That any of the concrete indices behind the source index names match dest.index
• That dest.index is NOT a simple regex pattern, and if it exists, is not backed by more than one index
• If the dest.index exists, that its concrete index is not contained in source.index concrete index names

Backport of #41803

[elasticmachine]

Pinging @elastic/ml-core

[benwtrent]

run elasticsearch-ci/1