Sync with Prism Launcher 8.0, rework custom account implementation #126

Job	Run time
Build Debug / flatpak	1m 51s
Build Debug / build (ubuntu-20.04, 5)	8m 15s
Build Debug / build (ubuntu-20.04, 6, linux, 6.2.4, qt5compat qtimageformats)	25m 10s
Build Debug / build (windows-2022, Windows-MinGW-w64, clang64, amd64_x86)	25m 22s
Build Debug / build (windows-2022, Windows-MSVC-Legacy, win32, amd64_x86, 5, windows, win32_msvc2019, 5.15.2, t...	10m 48s
Build Debug / build (windows-2022, Windows-MSVC, x64, amd64, 6, windows, 6.5.2, qt5compat qtimageformats)	35m 59s
Build Debug / build (windows-2022, Windows-MSVC-arm64, arm64, amd64_arm64, 6, windows, win64_msvc2019_arm64, 6....	20m 54s
Build Debug / build (macos-12, macOS, 11, 6, mac, 6.5.2, qt5compat qtimageformats)	35m 8s
Build Debug / build (macos-12, macOS-Legacy, 10.13, 5, mac, 5.15.2)	14m 24s
	2h 57m 51s

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