Auto merge of #99174 - scottmcm:reoptimize-layout-array, r=joshtriplett

Reoptimize layout array

This way it's one check instead of two, so hopefully (cc #99117) it'll be simpler for rustc perf too 🤞

Quick demonstration:
```rust
pub fn demo(n: usize) -> Option<Layout> {
    Layout::array::<i32>(n).ok()
}
```

Nightly: <https://play.rust-lang.org/?version=nightly&mode=release&edition=2021&gist=e97bf33508aa03f38968101cdeb5322d>
```nasm
	mov	rax, rdi
	mov	ecx, 4
	mul	rcx
	seto	cl
	movabs	rdx, 9223372036854775805
	xor	esi, esi
	cmp	rax, rdx
	setb	sil
	shl	rsi, 2
	xor	edx, edx
	test	cl, cl
	cmove	rdx, rsi
	ret
```

This PR (note no `mul`, in addition to being much shorter):
```nasm
	xor	edx, edx
	lea	rax, [4*rcx]
	shr	rcx, 61
	sete	dl
	shl	rdx, 2
	ret
```

This is built atop `@CAD97` 's #99136; the new changes are cb8aba66ef6a0e17f08a0574e4820653e31b45a0.

I added a bunch more tests for `Layout::from_size_align` and `Layout::array` too.

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