Cranelift: Add instructions for getting the current stack/frame/return pointers (#4573)

* Cranelift: Add instructions for getting the current stack/frame pointers and return address

This is the initial part of https://github.com/bytecodealliance/wasmtime/issues/4535

* x64: Remove `Amode::RbpOffset` and use `Amode::ImmReg` instead

We just special case getting operands from `Amode`s now.

* Fix s390x `get_return_address`; require `preserve_frame_pointers=true`

* Assert that `Amode::ImmRegRegShift` doesn't use rbp/rsp

* Handle non-allocatable registers in Amode::with_allocs

* Use "stack" instead of "r15" on s390x

* r14 is an allocatable register on s390x, so it shouldn't be used with `MovPReg`

cranelift/codegen/src/isa/aarch64/lower_inst.rs

@@ -53,6 +53,10 @@ pub(crate) fn lower_insn_to_regs<C: LowerCtx<I = Inst>>(
             point, as constants are rematerialized at use-sites"
         ),
 
+        Opcode::GetFramePointer | Opcode::GetStackPointer | Opcode::GetReturnAddress => {
+            implemented_in_isle(ctx)
+        }
+
         Opcode::Iadd => implemented_in_isle(ctx),
         Opcode::Isub => implemented_in_isle(ctx),
         Opcode::UaddSat | Opcode::SaddSat | Opcode::UsubSat | Opcode::SsubSat => {