VideoCommon: asset load time is now stored as a chrono system_clock time

[iwubcode]

This allows me to fabricate times (without creating a file) in a future feature.

Unfortunately, only windows (VS) supports clock_cast which is needed to convert file times to a system clock. I have implemented an approximation for other systems. Users on Linux/Mac/Android would need to test texture packs to make sure this doesn't break existing behavior (in particular the auto reloading which is used for Dynamic Input Textures).

[iwubcode]

Just a note for the record. This was tested on Android by @t895 with a texture pack. This was tested by a user in the DIT community on MacOS ARM using a DIT pack (to verify reloading). Not seeing any concerns merging this.

[MayImilae]

This PR was mentioned in https://bugs.dolphin-emu.org/issues/13352

[iwubcode]

Thanks @MayImilae . TryTwo/Spin2Win reached out to me. The old version of Windows just needs to use the same approach as the other backends that don't currently use clock_cast. I'm not sure offhand how to target just the old windows versions but I imagine it'll be relatively simple. Will open a PR sometime this weekend.

[AdmiralCurtiss]

You'd have to detect the existence of clock_cast at runtime, since we only ship a single Windows build for all Windows platforms. It's probably just easier to disable clock_cast until we drop the older Windows 10 versions...

[iwubcode]

Thanks Admiral, that's the same conclusion I came to unfortunately.