Cranelift: update to latest regalloc2: (#4324)

- Handle call instructions' clobbers with the clobbers API, using RA2's
  clobbers bitmask (bytecodealliance/regalloc2#58) rather than clobbers
  list;

- Pull in changes from bytecodealliance/regalloc2#59 for much more sane
  edge-case behavior w.r.t. liverange splitting.

cranelift/codegen/src/isa/aarch64/inst/emit_tests.rs

@@ -5286,8 +5286,9 @@ fn test_aarch64_binemit() {
         Inst::Call {
             info: Box::new(CallInfo {
                 dest: ExternalName::testcase("test0"),
-                uses: Vec::new(),
-                defs: Vec::new(),
+                uses: smallvec![],
+                defs: smallvec![],
+                clobbers: PRegSet::empty(),
                 opcode: Opcode::Call,
                 caller_callconv: CallConv::SystemV,
                 callee_callconv: CallConv::SystemV,
@@ -5301,8 +5302,9 @@ fn test_aarch64_binemit() {
         Inst::CallInd {
             info: Box::new(CallIndInfo {
                 rn: xreg(10),
-                uses: Vec::new(),
-                defs: Vec::new(),
+                uses: smallvec![],
+                defs: smallvec![],
+                clobbers: PRegSet::empty(),
                 opcode: Opcode::CallIndirect,
                 caller_callconv: CallConv::SystemV,
                 callee_callconv: CallConv::SystemV,