Rollup merge of #134140 - compiler-errors:unsafe-binders-ast, r=oli-obk

Add AST support for unsafe binders

I'm splitting up #130514 into pieces. It's impossible for me to keep up with a huge PR like that. I'll land type system support for this next, probably w/o MIR lowering, which will come later.

r? `@oli-obk`
cc `@BoxyUwU` and `@lcnr` who also may want to look at this, though this PR doesn't do too much yet

compiler/rustc_span/src/symbol.rs

@@ -2105,6 +2105,7 @@ symbols! {
         unreachable_macro,
         unrestricted_attribute_tokens,
         unsafe_attributes,
+        unsafe_binders,
         unsafe_block_in_unsafe_fn,
         unsafe_cell,
         unsafe_cell_raw_get,
@@ -2128,6 +2129,7 @@ symbols! {
         unwind_attributes,
         unwind_safe_trait,
         unwrap,
+        unwrap_binder,
         unwrap_or,
         use_extern_macros,
         use_nested_groups,
@@ -2186,6 +2188,7 @@ symbols! {
         windows,
         windows_subsystem,
         with_negative_coherence,
+        wrap_binder,
         wrapping_add,
         wrapping_div,
         wrapping_mul,