Properly block SDL IME results sent as multiple text events + upstream SDL fixes

[Susko3]

Depends on:

• SDL bump (for IME Composition Truncation + SDL_IsTextInputShown + SDL_ClearComposition libsdl-org/SDL#5398)

Closes ppy/osu#17231.

SDL will now send multiple SDL_TEXTINPUT events when the result is over 32 bytes. Here that is handled by blocking all text events that come in the same event loop. But because valid non-IME text events can arrive in the same event loop, we must check the text matches.

Eg. on Korean IME, pressing t, h, then 1: (only "소" is part of the composition, "1" is just regular text input)

// first event poll, pressing 't'
INFO: SDL EVENT: SDL_TEXTEDITING (timestamp=78142 windowid=1 text='ㅅ' start=1 length=0)

// second, pressing 'h'
INFO: SDL EVENT: SDL_TEXTEDITING (timestamp=78208 windowid=1 text='소' start=1 length=0)

// third, pressing '1'
// notice the two SDL_TEXTINPUTs
INFO: SDL EVENT: SDL_TEXTEDITING (timestamp=78736 windowid=1 text='' start=0 length=0)
INFO: SDL EVENT: SDL_TEXTEDITING (timestamp=78737 windowid=1 text='' start=0 length=0)
INFO: SDL EVENT: SDL_TEXTINPUT (timestamp=78737 windowid=1 text='소')
INFO: SDL EVENT: SDL_KEYDOWN (timestamp=78737 windowid=1 state=pressed repeat=false scancode=30 keycode=49 mod=4096)
INFO: SDL EVENT: SDL_TEXTINPUT (timestamp=78737 windowid=1 text='1')

[peppy]

Not tested, but code looks fine so let's get this merged for user testing.