Auto merge of rust-lang#136897 - workingjubilee:revert-unfcped-stab, r=WaffleLapkin

Revert "Stabilize `extended_varargs_abi_support`"

I cannot find an FCP for this, despite it being a stabilization PR which normally means we do an FCP of some kind? It would seem reasonable for _either_ compiler or lang to have FCPed it? I am thus opening a revert PR, which mostly-cleanly applies, so that we can later actually land this properly with a stability report and FCP.

- rust-lang#136896
- rust-lang#116161
- rust-lang#100189

Author: bors

std/src/lib.rs

@@ -272,6 +272,9 @@
 //
 // Language features:
 // tidy-alphabetical-start
+
+// stabilization was reverted after it hit beta
+#![cfg_attr(not(bootstrap), feature(extended_varargs_abi_support))]
 #![feature(alloc_error_handler)]
 #![feature(allocator_internals)]
 #![feature(allow_internal_unsafe)]