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* Remove outdated SVG and dot file from docs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/filetests/filetests/runtests/fdemote.clif

@@ -71,19 +71,16 @@ block0(v0: f64):
 
 
 ;; Tests a fdemote+load combo which some backends may optimize
-function %fdemote_load(i64 vmctx, i64, f64) -> f32 {
-    gv0 = vmctx
-    gv1 = load.i64 notrap aligned gv0+0
-    heap0 = static gv1, min 0x10, bound 0x10, offset_guard 0x0, index_type i64
+function %fdemote_load(i64, f64) -> f32 {
+    ss0 = explicit_slot 16
 
-block0(v0: i64, v1: i64, v2: f64):
-    v3 = heap_addr.i64 heap0, v1, 0, 8
+block0(v1: i64, v2: f64):
+    v3 = stack_addr.i64 ss0
     store.f64 v2, v3
     v4 = load.f64 v3
     v5 = fdemote.f32 v4
     return v5
 }
-; heap: static, size=0x10, ptr=vmctx+0, bound=vmctx+8
 ; run: %fdemote_load(0, 0x0.0) == 0x0.0
 ; run: %fdemote_load(1, 0x0.1) == 0x0.1
 ; run: %fdemote_load(2, 0x0.2) == 0x0.2