gl_shader_manager: Fix interaction between graphics and compute

After a compute shader was set to the pipeline, no graphics shader was
invoked again. To address this use glUseProgram to bind compute shaders
(without state tracking) and call glUseProgram(0) when transitioning out
of it back to the graphics pipeline.

cubeb_sink: Don't discard other channels when performing downmixing

video_core: Remove gl_state and use a state tracker based on dirty flags

textures: Fix anisotropy hack

Previous code could generate an anisotropy value way higher than x16.

Previously, when performing downmixing, we would discard all channels except the left and right one.
This implementation respects them when mixing down to Stereo.
It is taken from this document: http://www.atsc.org/wp-content/uploads/2015/03/A52-201212-17.pdf.

Fixes Luigis Mansion 3 cutscene and Bayonetta audio.

frontend/Graphics: Add "Advanced" graphics tab and experimental Anisotropic Filtering support

maxwell_to_vk: Remove Storage capability for A1B5G5R5U

vk_swapchain: Silence TOCTOU race condition

Minor fixes for udp input

vk_shader_decompiler: Implement indexed textures

shader_decode: Fix LD, LDG when track constant buffer

Refactoring to boot A32 games

video_core: Implement more scaled attribute formats

When the default file is read in, the settings default value is only used
when the key is missing. As it was, the key existed, but the value was empty string
causing it to accept that as a value to pass into the core

ARM_Interface: Cache the JITs instead of deleting/recreating.

Port citra-emu/citra#5097: "Update README.md"

audio_core: interpolate: Improvements to fix audio crackling.

Blending doesn't affect blits. Rasterizer discard does, update the
commentaries.

Blending doesn't affect clears.