Implement operation element-of expression

[rascmatt]

Implements type checking and behavior lowering for the element-of (∈) and no-element-of (∉) binary operators within the [assert : ...] and [stop : ...] annotations of group expressions.

Since operation definitions are sets of instructions, the semantics of the element-of operators behaves as expected like the element-of operator of a set. To the left side of the expression we allow a reference to some captured instruction, either bound via an exist .. then or forall .. then expression index, or via a group reference.

Examples:

VLIW(0) ∈ ALU_FP
i ∈ ALU_FP

This is the last remaining piece for the group expression/annotations required for VLIW support, so I re-enabled those in the hexagon.vadl spec. This required some slight adaptions, to use the logical or/and operators (||, &&) rather than the bitwise operators.

[rascmatt]

As discussed with @AndreasKrall in our weekly meeting today, the in and !in operators are expected to be alternatives to the ∈ and ∉, so I will extend the frontend with that.