[Remote Store] Add allocation decider for mixed cluster

[ltaragi]

Is your feature request related to a problem? Please describe

A new allocation decider for migration of document replication clusters to remote store backed clusters.

Describe the solution you'd like

• For STRICT compatibility mode, the decision is always YES
• For remote_store_enabled indices, relocation or allocation/relocation can only be towards a remote node
• For REMOTE_STORE migration direction:
  • New primary shards can only be allocated to a remote node
  • New replica shards can be allocated to a remote node iff the primary has been migrated/allocated to a remote node

Related component

Storage:Remote

Describe alternatives you've considered

No response

Additional context

No response