remove type coercion from array values to references

* Implements #3768. This is a sweeping breaking change that requires
   many (trivial) edits to Zig source code. Array values no longer
   coerced to slices; however one may use `&` to obtain a reference to
   an array value, which may then be coerced to a slice.

 * Adds `IrInstruction::dump`, for debugging purposes. It's useful to
   call to inspect the instruction when debugging Zig IR.

 * Fixes bugs with result location semantics. See the new behavior test
   cases, and compile error test cases.

 * Fixes bugs with `@typeInfo` not properly resolving const values.

 * Behavior tests are passing but std lib tests are not yet. There
   is more work to do before merging this branch.

lib/std/priority_queue.zig

@@ -22,7 +22,7 @@ pub fn PriorityQueue(comptime T: type) type {
         /// `fn lessThan(a: T, b: T) bool { return a < b; }`
         pub fn init(allocator: *Allocator, compareFn: fn (a: T, b: T) bool) Self {
             return Self{
-                .items = [_]T{},
+                .items = &[_]T{},
                 .len = 0,
                 .allocator = allocator,
                 .compareFn = compareFn,