[Remote Store] Introduce validation of index template for restricted remote store backed indices

[ashking94]

Is your feature request related to a problem? Please describe.
Today, we allow index template creation and skip doing validation which can lead to issues when the index creation is happening though the index template. We need to introduce validation to ensure we do not allow creating such index templates that will ultimately fail to execute.

Describe the solution you'd like
Validate index template creation.

Describe alternatives you've considered
Validate combined template settings at the time of index creation.

Additional context
Add any other context or screenshots about the feature request here.

[Bukhtawar]

Validations need to be added for restricted remote store backed indices.

[Storage Triage - attendees 1 2 3 4 5 6 7 8 9 10

[sonu4578]

@sachinpkale @Bukhtawar Hi Sachin, Bukhtawar, I can create a PR to add the validation for restricted remote store backed indices.

Could you please assign this issue to me?

Could you please also share the context of the code that creates the restricted remote store backed indices and the validation steps that need to be added?

[sachinpkale]

@sachinpkale @Bukhtawar Hi Sachin, Bukhtawar, I can create a PR to add the validation for restricted remote store backed indices.

Thanks @sonu4578 . Assigning this to you.

@ashking94 can provide more details on the validations to be added.