[wgsl-in] Incorrect handling of negative integers with hex values

[Wumpf]

The following isn't accepted right now (note that this is how the spec defines the minimum integer https://www.w3.org/TR/WGSL/#integer-types)

const i32min = i32(-0x80000000);

Instead this is accepted and probably shouldn't:

const i32min = -0x80000000i

In fact, Tint will fail this with:

Tint WGSL reader failure: :24:17 error: value cannot be represented as 'i32'
const i32min = -0x80000000i; // Tint can't handle this being represented as `-0x80000000i`

I thought originally that this is the actual error, but I think the reasoning over at the chrome bug I opened is correct and above should be rejected, see https://bugs.chromium.org/p/chromium/issues/detail?id=1439274

For anyone else running into this, note that const i32min = -2147483648; is accepted by both compilers.

[teoxoy]

gfx-rs/naga#1863 fixed us not accepting:

const i32min = i32(-0x80000000);

---

const i32min = -0x80000000i;

Still works and shouldn't but will be fixed with #4400 since we currently treat the minus as part of the number when tokenizing.

[jimblandy]

With #4870, this works:

const i32min = i32(-0x80000000);

and this gets an error:

const i32min = -0x80000000i;

Now Naga says:

error: numeric literal not representable by target type: `0x80000000i`
  ┌─ min.wgsl:2:17
  │
2 │ const i32min = -0x80000000i;
  │                 ^^^^^^^^^^^ numeric literal not representable by target type

So I think this one should be fixed by that PR.