This is all of the expected 0.14.0 progress on #21530, which can now be
postponed once this commit is merged.
This required rewriting the (un)wrap operations since the original
implementations were extremely buggy.
Also adds an easy way to retrigger Sema OPV bugs so that I don't have to
keep updating #22419 all the time.
This makes `0123` and `u0123` etc. illegal.
I'm now confident that this is a good change because
I actually caught two C header translation mistakes in `haiku.zig` with this.
Clearly, `0123` being octal in C (TIL) can cause confusion, and we make this easier to read by
requiring `0o` as the prefix and now also disallowing leading zeroes in integers.
For consistency and because it looks weird, we disallow it for integer types too (e.g. `u0123`).
Fixes#11963Fixes#12417
