layout.might_permit_raw_init supports additional checks

[tedinski]

Rust's layout.might_permit_raw_init went from taking true/false flag to taking:

1. InitKind::Zero, * which corresponds to the old true (and the intrinsic assert_zero_valid)
2. InitKind::Uninit, false which corresponds to the old false (and the instrinsic assert_uninit_valid)
3. InitKind::Uninit, false which adds an additional strict check. Unclear if we want it for something.

Upstream PR: rust-lang/rust#97323

[adpaco]

In the most recent update, Rust provides two methods permits_zero_init and permits_uninit_init for the type context (where layout is the argument) instead of the method might_permit_raw_init for layouts.

The updates to the intrinsics code in #1399 make use of them (as in the ssa and cranelift backends), so there's nothing else to do here.