Cranelift: Add heap_load and heap_store instructions (#5300)

* Cranelift: Define `heap_load` and `heap_store` instructions

* Cranelift: Implement interpreter support for `heap_load` and `heap_store`

* Cranelift: Add a suite runtests for `heap_{load,store}`

There are so many knobs we can twist for heaps and I wanted to exhaustively test
all of them, so I wrote a script to generate the tests. I've checked in the
script in case we want to make any changes in the future, but I don't think it
is worth adding this to CI to check that scripts are up to date or anything like
that.

* Review feedback

cranelift/codegen/src/verifier/mod.rs

@@ -64,6 +64,7 @@ use crate::entity::SparseSet;
 use crate::flowgraph::{BlockPredecessor, ControlFlowGraph};
 use crate::ir;
 use crate::ir::entities::AnyEntity;
+use crate::ir::immediates::HeapImmData;
 use crate::ir::instructions::{BranchInfo, CallInfo, InstructionFormat, ResolvedConstraint};
 use crate::ir::{
     types, ArgumentPurpose, Block, Constant, DynamicStackSlot, FuncRef, Function, GlobalValue,
@@ -678,6 +679,10 @@ impl<'a> Verifier<'a> {
             UnaryGlobalValue { global_value, .. } => {
                 self.verify_global_value(inst, global_value, errors)?;
             }
+            HeapLoad { heap_imm, .. } | HeapStore { heap_imm, .. } => {
+                let HeapImmData { heap, .. } = self.func.dfg.heap_imms[heap_imm];
+                self.verify_heap(inst, heap, errors)?;
+            }
             HeapAddr { heap, .. } => {
                 self.verify_heap(inst, heap, errors)?;
             }