Unrolled build for rust-lang#134367

Rollup merge of rust-lang#134367 - WaffleLapkin:trait_upcasting_as_a_treat, r=compiler-errors

Stabilize `feature(trait_upcasting)`

This feature was "done" for a while now, I think it's finally time to stabilize it! Stabilization report: rust-lang#134367 (comment).
cc reference PR: rust-lang/reference#1622.

Closes rust-lang#65991 (tracking issue), closes rust-lang#89460 (the lint is no longer future incompat).

r? compiler-errors

Author: rust-timer

tests/ui/dyn-star/upcast.rs

@@ -1,6 +1,6 @@
 //@ known-bug: #104800
 
-#![feature(dyn_star, trait_upcasting)]
+#![feature(dyn_star)]
 
 trait Foo: Bar {
     fn hello(&self);

tests/ui/dyn-star/upcast.stderr

@@ -1,7 +1,7 @@
 warning: the feature `dyn_star` is incomplete and may not be safe to use and/or cause compiler crashes
   --> $DIR/upcast.rs:3:12
    |
-LL | #![feature(dyn_star, trait_upcasting)]
+LL | #![feature(dyn_star)]
    |            ^^^^^^^^
    |
    = note: see issue #102425 <https://github.com/rust-lang/rust/issues/102425> for more information