maxwell_3d: Allow texture handles with TIC id zero

gl_rasterizer: Use DSA for textures and move swizzling to texture state

Port citra-emu/citra#4586: "Use QPixmap/QIcon for background color selection button"

Port citra-emu/citra#4583: "citra_qt: Fix saving screenshot when no file extension is provided"

service/nvflinger, service/vi: Improve error case handling

QT: Fix the loading screen 'H' switch logo to not glitch out

Converts many of the Find* functions to return a std::optional<T> as
opposed to returning the raw return values directly. This allows
removing a few assertions and handles error cases like the service
itself does.

video_core/texture: Fix BitField size for depth_minus_one

This member function doesn't actually modify instance state, so it can
be marked as a const member function.

This was missed within #2075. Renames the member function to make it
consistent with the rest of the Find* functions.

 shader_ir/memory: Add LD_L 64 bits loads 

Fix TXQ not using the component mask.

Co-Authored-By: FernandoS27 <fsahmkow27@gmail.com>

Also remove "enabled" field from Tegra::Texture::FullTextureInfo because
it would become unused.