[RW Separation] Updates to restore from snapshot with added search replicas

[mch2]

With #15368 we add the ability to create and update an index to have search replicas. We need to also support this configuration on restore. With this issue we should accomplish this while honoring the same validations for search replicas:

1. Search replicas allowed with Segrep only
2. Auto expand replica count not allowed
3. Feature flag enforced

[vinaykpud]

Hi @mch2
I would like to pickup this issue