swift

d04fff6f - A @_distributedActorIndependent declaration is nonisolated.

A @_distributedActorIndependent declaration is nonisolated. The `@__distributedActorIndependent` attribute is effectively the same as nonisolated, so start treating it that way by making actor-isolation checking look for it specifically and conclude "nonisolated". Remove various special cases for this attribute that don't need to exist.