Compare slicing expression types to avoid promotion in Array View Elision support code

[e-kayrakli]

A statement like

Arr1[1..9] = Arr2[{1..9}];

resulted in doing something akin to

1..9 == {1..9};

which is a promoted expression. That caused some resolution errors downstream. This PR compares chpl__protoSlice types before doing the comparison that resulted in promotion to prevent that.

Test:

• linux64
• gasnet