Auto merge of #112244 - RalfJung:miri, r=oli-obk

update Miri

Also adjust Miri's compiletest a little: in pre-subtree days we added `-A unused -Astable-features` to have the Miri toolstate break less often. But nowadays it just causes confusion when Miri CI works in rustc but fails on the Miri side so let's get rid of this difference.

r? `@oli-obk`