Handle SDL joypad events for connected controllers on game startup (on Windows and Linux)

[Nintorch]

Fixes #109717

Make sure that SDL events are processed when the SDL joypad input driver is initialized, this will allow it to register the connected controllers when the game starts. The registered controllers will then show up in Input.get_connected_joypads().

Before this PR

After this PR

I tested this PR on Windows and I thought this would fix it on all platforms 😅
TODO:

• Fix this PR on macOS (the issue is also reproducible in Godot 4.4.1, so not technically a bug in this PR, I've read somewhere that it's a quirk of Apple's API)
• Check if it fixes the issue on Linux

[bruvzg]

Tested it on macOS, I can reproduce the issue, but this change doesn't fix it.

[Nintorch]

Thank you for testing, bruvzg! I will try to reproduce the issue tomorrow on macOS myself and I will try to fix it!

[bruvzg]

Most likely, it needs a system event pump (DisplayServer::process_events) to run to work.

[spookto]

Tested on Linux (CachyOS) and it fixes the bug.

[Calinou]

Code looks good to me.

[Nintorch]

Thank you for testing, spookto and Calinou!

[Nintorch]

@naturally-intelligent Sorry for bothering you, may I ask if this change fixes your issue?

[bruvzg]

Seems like in case of macOS it is detected after 5-10 main event loop iterations, so not sure if it's even fixable (or should be considered a bug at all).

[Nintorch]

May I ask if the issue is also reproducible in Godot 4.4 on macOS?

[bruvzg]

Yes, it is the same 4.4.1.

[Nintorch]

I see, thank you for testing!

[bruvzg]

Tested in on Linux and Windows, in both cases issue is reproducible and fixed.

[Repiteo]

Thanks!

[Nintorch]

Thank you! :D

[harrisyu]

With this merge,, my gampad is not working, and with following message:

E 0:00:00:435   JoypadSDL::process_events: Error opening gamepad at index 1: IDirectInputDevice8::SetCooperativeLevel() DirectX error 0x80070006
  <C++ Error>   Condition "!gamepad" is true. Continuing.
  <C++ Source>  drivers\sdl\joypad_sdl.cpp:141 @ JoypadSDL::process_events()

Gamepad works again after revert it.
BTW, my OS = Windows 11, controller = 8 Bitdo - Ultimate C Wired Controller.

[Nintorch]

Oops, I forgot about DInput controllers 😅 I will try to fix the problem

[naturally-intelligent]

Fix works for me (as of beta7)
Thanks!