Backport of #62527 to 7.x branch.
This commit adds validation that prohibits the creation of regular indices
in the namespace of templates with data streams enabled.
It shouldn't be possible to create ordinary indices when the name of the index
matches with a composable index template that enables data streams. Auto creation
has logic that creates data streams instead of regular indices. However validation
logic for the create index api was missing.
5f643433c6