reference: refactor & fix matching of cyclical refs

[radeksimko]

This introduces some minor changes to the interfaces, to plumb context through, in preparation for using it to pass down context, such as whether "SelfRefs" is active, i.e. whether self.* addresses are relevant in that context.

Additionally, the matching logic is being refactored and updated to account for cyclical references, specifically to continue rejecting completion such as

resource "aws_instance" "test" {
  count = 4

  cpu_core_count = aws_instance.test.cpu_core_count
}

TODO: Address hover & semtok highlighting which still recognize the above as valid ^

and

resource "aws_instance" "test" {
  count = count.index
}

and (future)

resource "aws_instance" "test" {
  ami = self.ami
}

[dbanck]

Nice! Thanks for extracting this