Externals: Update fmt to 9.1.0

[Pokechu22]

This is mostly a test; I'm not aware of any benefits of updating at this time.

[lioncash]

Generally, you'd want to update anyway, since fmt 9.0.0 deprecates implicitly converting unscoped/regular enums into ints to make behavior consistent with scoped enum behavior. So all updating later does is potentially make things break since the deprecated facilities will likely be removed outright on the next major version.

[Pokechu22]

fmt 9.0.0 deprecates implicitly converting unscoped/regular enums into ints to make behavior consistent with scoped enum behavior

Indeed, that seems to be the cause of most of the errors. I've worked around that for now (mostly by excessive casts - I can convert to EnumFormatter later).

The other issue is that Qt creates a uint typedef in the global namespace, which ends up being shadowed by this in fmt. I've worked around this by disabling the warning, but I'm not sure of a better solution (I don't think we can move Qt to a separate namespace using QT_NAMESPACE easily since that would break shared libraries.)

[shuffle2]

we have a fix for this in fmt, please keep it

[Pokechu22]

Ah, I didn't see them because they weren't listed as patch files... I assume 357dc72 and 7b8e6c5?

[shuffle2]

yup

[Pokechu22]

Looks like 357dc72 isn't needed anymore, but I was able to cherry-pick 7b8e6c5 and it seems to work.

[lioncash]

Is this good to be merged?

[Pokechu22]

Theoretically there could be some additional enums converted to enum classes, but that can also be done later on (and some of these, such as the IOS error codes, are trickier to change). So this is probably good to go now.

We can't convert fmt to a submodule yet due to the extra patch. However, it looks like an equivalent same patch was adopted as fmtlib/fmt#3137, so we'd be able to use a submodule after that (although maybe fmt.vcxproj would still cause issues?)