Bump regalloc2 to 0.7.0 (#6237)

* Bump RA2 to 0.7.0

* Certify the RA2 update

* Import the rustc-hash audit

* Updates for regalloc2

prtest:full

* Update tests

cranelift/codegen/src/isa/x64/inst/regs.rs

@@ -203,6 +203,7 @@ pub(crate) fn create_reg_env_systemv(flags: &settings::Flags) -> MachineEnv {
             vec![],
         ],
         fixed_stack_slots: vec![],
+        scratch_by_class: [None, None],
     };
 
     debug_assert_eq!(r15(), pinned_reg());