Rollup merge of #128592 - evelynharthbrooke:master, r=Mark-Simulacrum

Promote aarch64-apple-darwin to Tier 1

This promotes aarch64-apple-darwin to Tier 1 status as per rust-lang/rfcs#3671 and tracking issue #73908. Not sure what else is necessary for this to impement the aforementioned RFC, however I figured I'd try. I did read in previous issues and PRs that the necessary infrastructure was already in place for the aarch64-apple-darwin target, and the RFC mentions the same. So this should be all thats necessary in order for the target to be promoted.

This is a recreation of my previous PR because I accidentally did an incorrect git rebase which caused unnecessary changes to various commit SHAs. So this PR is a recreation of my previous PR without said stumble. My bad.

README.md

@@ -212,7 +212,6 @@ degree documented below):
 - All Rust [Tier 1 targets](https://doc.rust-lang.org/rustc/platform-support.html) are supported by
   Miri. They are all checked on Miri's CI, and some (at least one per OS) are even checked on every
   Rust PR, so the shipped Miri should always work on these targets.
-- `aarch64-apple-darwin` is supported.
 - `s390x-unknown-linux-gnu` is supported as our "big-endian target of choice".
 - For every other target with OS `linux`, `macos`, or `windows`, Miri should generally work, but we
   make no promises and we don't run tests for such targets.

ci/ci.sh

@@ -137,7 +137,7 @@ case $HOST_TARGET in
     MANY_SEEDS=16 TEST_TARGET=x86_64-pc-windows-gnu run_tests
     ;;
   aarch64-apple-darwin)
-    # Host (tier 2)
+    # Host
     GC_STRESS=1 MIR_OPT=1 MANY_SEEDS=64 TEST_BENCH=1 CARGO_MIRI_ENV=1 run_tests
     # Extra tier 1
     MANY_SEEDS=64 TEST_TARGET=i686-pc-windows-gnu run_tests