Transition to SDL3

[portaloffreedom]

SDL3 is not release yet, but has hit ABI freeze. Until it's officially released this PR should not be merged.

[portaloffreedom]

Currently SDL3 is being installed the hard way (git clone; make; sudo make install), we need to come up with a plan for this to change. Possible alternatives:

• vendor sdl inside the project statically
• vendor sdl inside the project, giving a dynamic library
• wait for sdl to be available in the next ubuntu LTS, which seems to be the most common denominator for old distros. (probably going to take 2 years or more)
• vendor SDL3 statically only for CI builds, but demand that developers that compile the code handle the problem of providing SDL3 themselves.

[metaleap]

wait for sdl to be available in the next ubuntu LTS, which seems to be the most common denominator for old distros. (probably going to take 2 years or more)

Another option is to "wait until SDL's Wikipedia page lists a 3.x as 'Stable Release' instead of the current 2.x" 😁 even libsdl.org lists 2.x as stable and 3.x as preview..

Early-adopting the bleeding edge is fine for self-contained solo indie game projects etc, but a many-users engine project like Wicked (with almost as many WIP projects) can let the-hot-new-thing settle into stabilization and even some maturation first =) when it comes to Wicked release versions, I mean — that you're already exploring SDL3 here is of course neato!

Vendoring: intuitively but without quite knowing explicitly why, I'd be wary about vendoring something like SDL the same way it's currently only done with LUA, Jolt, FAudio etc. It's such a common "system-wide dep".. and if one's Wicked Game C++ app ever imports anything else that also references SDL but the system one (or its own static or shared vendored one... 😵‍💫 ), even if only to "optionally support" it (say some immediate-mode-GUI lib or other, who knows), at best you have the whole codebase loaded twice in memory and at worst maybe people get link-time conflicts / version differences, duplicate symbols or who knows what build-time or run-time confusions?