Enable permissive provenance by default
This completes the plan laid out in https://github.com/rust-lang/miri/issues/2133:
- We use permissive provenance with wildcard pointers by default.
- We print a warning on int2ptr casts. `-Zmiri-permissive-provenance` suppresses the warning; `-Zmiri-strict-provenance` turns it into a hard error.
- Raw pointer tagging is now always enabled, so we remove the `-Zmiri-tag-raw-pointers` flag and the code for untagged pointers. (Passing the flag still works, for compatibility -- but we just ignore it, with a warning.)
We also fix an intptrcast issue:
- Only live allocations are considered when computing the AllocId from an address.
So, finally, Miri has a good story for ptr2int2ptr roundtrips *and* no weird false negatives when doing raw pointer stuff with Stacked Borrows. :-) 🎉 Thanks a lot to everyone who helped with this, in particular `@carbotaniuman` who convinced me this is even possible.
Fixes https://github.com/rust-lang/miri/issues/2133
Fixes https://github.com/rust-lang/miri/issues/1866
Fixes https://github.com/rust-lang/miri/issues/1993
7fafbde038