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/write.rs

@@ -5,6 +5,7 @@
 
 use crate::entity::SecondaryMap;
 use crate::ir::entities::AnyEntity;
+use crate::ir::immediates::{HeapImmData, Uimm32};
 use crate::ir::{Block, DataFlowGraph, Function, Inst, SigRef, Type, Value, ValueDef};
 use crate::packed_option::ReservedValue;
 use alloc::string::{String, ToString};
@@ -476,6 +477,47 @@ pub fn write_operands(w: &mut dyn Write, dfg: &DataFlowGraph, inst: Inst) -> fmt
             dynamic_stack_slot,
             ..
         } => write!(w, " {}, {}", arg, dynamic_stack_slot),
+        HeapLoad {
+            opcode: _,
+            heap_imm,
+            arg,
+        } => {
+            let HeapImmData {
+                flags,
+                heap,
+                offset,
+            } = dfg.heap_imms[heap_imm];
+            write!(
+                w,
+                " {heap} {flags} {arg}{optional_offset}",
+                optional_offset = if offset == Uimm32::from(0) {
+                    "".to_string()
+                } else {
+                    format!("+{offset}")
+                }
+            )
+        }
+        HeapStore {
+            opcode: _,
+            heap_imm,
+            args,
+        } => {
+            let HeapImmData {
+                flags,
+                heap,
+                offset,
+            } = dfg.heap_imms[heap_imm];
+            let [index, value] = args;
+            write!(
+                w,
+                " {heap} {flags} {index}{optional_offset}, {value}",
+                optional_offset = if offset == Uimm32::from(0) {
+                    "".to_string()
+                } else {
+                    format!("+{offset}")
+                }
+            )
+        }
         HeapAddr {
             heap,
             arg,