Migrate Lime on native platforms to use SDL3

[EliteMasterEric]

SDL just released version 3.1.3 stable API preview, which means that (while the library still has bugs and issues to resolve before the 3.2 stable release), no existing functions will be removed, making it stable enough for migration.

There is a very long list of useful features that migrating would enable (see the list at the link), and also a long list of issues that are resolved by updating (such as #1569), but this first requires migrating the existing places that SDL2 are used.

I originally attempted this myself by just editing the existing implementation last year, but this resulted in a bunch of graphical glitches, so updating would probably require someone more experienced with C++ and graphics APIs.

[EliteMasterEric]

Some features we may find relevant (now or in the future) include:

• Using nanoseconds for timestamps in various places
• Using OS timestamps for input events (rather than the SDL timestamp, making it way more accurate)
• Replacing TinyFileDialog with a more flexible and well-maintained implementation
• Support for clipboard data of any mime type
• Improved audio stream handling
• New storage and file-system APIs that work across platforms
• The new SDL Graphics API, providing access to cross-platform graphics and compute.

Plus any fixes from newer versions of SDL 2.x.