Auto merge of #91569 - erikdesjardins:vt-align, r=nikic

Auto merge of #91569 - erikdesjardins:vt-align, r=nikic

Attach range metadata to alignment loads from vtables

...because alignment is always nonzero[0].

This helps eliminate redundant runtime alignment checks, when a DST
is a field of a struct whose remaining fields have alignment 1.

Fixes #91438.

---
[0]:

The [reference](https://doc.rust-lang.org/reference/type-layout.html) says that alignment must be at least 1.

And in practice, the alignment field for all vtables is generated here: https://github.com/rust-lang/rust/blob/772d51f887fa407216860bf8ecf3f1a32fb795b4/compiler/rustc_middle/src/ty/vtable.rs#L68-L90 and is nonzero because [`Align::bytes()`](https://github.com/rust-lang/rust/blob/772d51f887fa407216860bf8ecf3f1a32fb795b4/compiler/rustc_target/src/abi/mod.rs#L547-L549) is always nonzero.