Auto merge of #29274 - thepowersgang:issues-29107-const-unsafe-fn-order, r=nikomatsakis

This PR switches the implemented ordering from `unsafe const fn` (as was in the original RFC) to `const unsafe fn` (which is what the lang team decided on)

src/test/compile-fail/unsafe-const-fn.rs

@@ -12,7 +12,7 @@
 
 #![feature(const_fn)]
 
-unsafe const fn dummy(v: u32) -> u32 {
+const unsafe fn dummy(v: u32) -> u32 {
     !v
 }
 

src/test/run-pass/const-unsafe-fn.rs

@@ -12,13 +12,13 @@
 
 #![feature(const_fn)]
 
-unsafe const fn dummy(v: u32) -> u32 {
+const unsafe fn dummy(v: u32) -> u32 {
     !v
 }
 
 struct Type;
 impl Type {
-    unsafe const fn new() -> Type {
+    const unsafe fn new() -> Type {
         Type
     }
 }