Auto merge of #34012 - eddyb:tick-erased, r=nikomatsakis

rustc: add ReErased to be used by trait selection, MIR and trans.

`ReErased` replaces `ReStatic` (i.e. `'static`) for erasing regions.
Using a distinct lifetime helps prevent accidental mix-ups between the two.
It also allows cleaner type printing (see test changes), including in symbol names:
```rust
str..pattern..CharSearcher$LT$$u27$static$GT$::drop.30560::h840c2f2afc03bbea // before
str..pattern..CharSearcher::drop.30561::h6bd31d2af614377a // after
```
Not that we should be producing symbols this way, but it's still better.

src/librustdoc/clean/mod.rs

@@ -827,7 +827,8 @@ impl Clean<Option<Lifetime>> for ty::Region {
             ty::ReScope(..) |
             ty::ReVar(..) |
             ty::ReSkolemized(..) |
-            ty::ReEmpty => None
+            ty::ReEmpty |
+            ty::ReErased => None
         }
     }
 }