Remove heaps from core Cranelift, push them into cranelift-wasm (#5386)

* cranelift-wasm: translate Wasm loads into lower-level CLIF operations

Rather than using `heap_{load,store,addr}`.

* cranelift: Remove the `heap_{addr,load,store}` instructions

These are now legalized in the `cranelift-wasm` frontend.

* cranelift: Remove the `ir::Heap` entity from CLIF

* Port basic memory operation tests to .wat filetests

* Remove test for verifying CLIF heaps

* Remove `heap_addr` from replace_branching_instructions_and_cfg_predecessors.clif test

* Remove `heap_addr` from readonly.clif test

* Remove `heap_addr` from `table_addr.clif` test

* Remove `heap_addr` from the simd-fvpromote_low.clif test

* Remove `heap_addr` from simd-fvdemote.clif test

* Remove `heap_addr` from the load-op-store.clif test

* Remove the CLIF heap runtest

* Remove `heap_addr` from the global_value.clif test

* Remove `heap_addr` from fpromote.clif runtests

* Remove `heap_addr` from fdemote.clif runtests

* Remove `heap_addr` from memory.clif parser test

* Remove `heap_addr` from reject_load_readonly.clif test

* Remove `heap_addr` from reject_load_notrap.clif test

* Remove `heap_addr` from load_readonly_notrap.clif test

* Remove `static-heap-without-guard-pages.clif` test

Will be subsumed when we port `make-heap-load-store-tests.sh` to generating
`.wat` tests.

* Remove `static-heap-with-guard-pages.clif` test

Will be subsumed when we port `make-heap-load-store-tests.sh` over to `.wat`
tests.

* Remove more heap tests

These will be subsumed by porting `make-heap-load-store-tests.sh` over to `.wat`
tests.

* Remove `heap_addr` from `simple-alias.clif` test

* Remove `heap_addr` from partial-redundancy.clif test

* Remove `heap_addr` from multiple-blocks.clif test

* Remove `heap_addr` from fence.clif test

* Remove `heap_addr` from extends.clif test

* Remove runtests that rely on heaps

Heaps are not a thing in CLIF or the interpreter anymore

* Add generated load/store `.wat` tests

* Enable memory-related wasm features in `.wat` tests

* Remove CLIF heap from fcmp-mem-bug.clif test

* Add a mode for compiling `.wat` all the way to assembly in filetests

* Also generate WAT to assembly tests in `make-load-store-tests.sh`

* cargo fmt

* Reinstate `f{de,pro}mote.clif` tests without the heap bits

* Remove undefined doc link

* Remove outdated SVG and dot file from docs

* Add docs about `None` returns for base address computation helpers

* Factor out `env.heap_access_spectre_mitigation()` to a local

* Expand docs for `FuncEnvironment::heaps` trait method

* Restore f{de,pro}mote+load clif runtests with stack memory

cranelift/codegen/src/write.rs

@@ -5,7 +5,6 @@
 
 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};
@@ -57,13 +56,6 @@ pub trait FuncWriter {
             self.write_entity_definition(w, func, gv.into(), gv_data)?;
         }
 
-        for (heap, heap_data) in &func.heaps {
-            if !heap_data.index_type.is_invalid() {
-                any = true;
-                self.write_entity_definition(w, func, heap.into(), heap_data)?;
-            }
-        }
-
         for (table, table_data) in &func.tables {
             if !table_data.index_type.is_invalid() {
                 any = true;
@@ -478,54 +470,6 @@ 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,
-            offset,
-            size,
-            ..
-        } => write!(w, " {}, {}, {}, {}", heap, arg, offset, size),
         TableAddr { table, arg, .. } => write!(w, " {}, {}", table, arg),
         Load {
             flags, arg, offset, ..