Rename cast_ref_to_mut lint to invalid_reference_casting

Author: Urgau

tests/fail/both_borrows/shr_frozen_violation1.rs

@@ -1,7 +1,7 @@
 //@revisions: stack tree
 //@[tree]compile-flags: -Zmiri-tree-borrows
 
-#![allow(cast_ref_to_mut)]
+#![allow(invalid_reference_casting)]
 
 fn foo(x: &mut i32) -> i32 {
     *x = 5;

tests/fail/modifying_constants.rs

@@ -1,7 +1,7 @@
 // This should fail even without validation/SB
 //@compile-flags: -Zmiri-disable-validation -Zmiri-disable-stacked-borrows
 
-#![allow(cast_ref_to_mut)]
+#![allow(invalid_reference_casting)]
 
 fn main() {
     let x = &1; // the `&1` is promoted to a constant, but it used to be that only the pointer is marked static, not the pointee