Auto merge of #128037 - beetrees:repr128-c-style-use-natvis, r=michaelwoerister

Use the `enum2$` Natvis visualiser for repr128 C-style enums

Use the preexisting `enum2$` Natvis visualiser to allow PDB debuggers to display fieldless `#[repr(u128)]]`/`#[repr(i128)]]` enums correctly.

Tracking issue: #56071

try-job: x86_64-msvc

Author: bors