Fixes the SDL input source's icon and name lookups for controllers SDL can't confidently brand. Unknown-type pads no longer default to PlayStation glyphs, and STANDARD, XBOX360, XBOXONE, and NINTENDO_SWITCH_PRO now each get their own button name table instead of falling back to generic "Face South"-style text.
This is visible in the Qt Controller Settings binding list, and as icons in FullscreenUI's Controller Settings and save-state legend.
Fixes three related bugs that broke button icons and layout detection for XInput controllers:
- XInputSource::ConvertKeyToIcon checked for the wrong source type (SDL instead of XInput) and never resolved icons.
- SDLInputSource reused generic/unbranded icons for Xbox 360/One controller types instead of proper Xbox glyphs.
- InputManager::PreprocessEvent always queried the SDL source for controller layout regardless of which source produced the event, causing FullscreenUI to fall back to PlayStation icons whenever SDL was disabled.
Move files from Frontend directory to pcsx2 and/or subdirectories.
Get rid of double GS init.
Combine HostSettings and Host.
Combine Frontend/Achievements.h and Achievements.h.