Add support for leaf fn frame pointer elimination

This PR adds ability for the target specifications to specify frame
pointer emission type that's not just “always” or “whatever cg decides”.

In particular there's a new mode that allows omission of the frame
pointer for leaf functions (those that don't call any other functions).

We then set this new mode for Aarch64-based Apple targets.

Fixes #86196

compiler/rustc_codegen_ssa/src/base.rs

@@ -406,7 +406,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         };
 
         // `main` should respect same config for frame pointer elimination as rest of code
-        cx.set_frame_pointer_elimination(llfn);
+        cx.set_frame_pointer_type(llfn);
         cx.apply_target_cpu_attr(llfn);
 
         let llbb = Bx::append_block(&cx, llfn, "top");