glsl_shader_decompiler: Minor API changes to ShaderWriter

ShaderGen: Fixed TEXS overriding its own texcoords and implemented fmul32i

This function doesn't need to take ownership of the string data being
given to it, considering all we do is append the characters to the
internal string instance.

Instead, use a string view to simply reference the string data without
any potential heap allocation.

Now anything that is a raw const char* won't need to be converted to a
std::string before appending.

Avoids constructing a std::string just to append a newline character

Avoids constructing a std::string just to append a character.

The interface of std::string already lets us append N copies of a
character to an existing string.

Technically, yuzu can boot commercial games

ShaderGen: Fixed a case where the TEXS instruction would use the same registers for the input and the output.

It will now save the coords before writing the outputs in a subscope.

Implement Pull #3528 from citra: use nvidia graphics automatically on laptops with optimus (with AMD support) (#271)

* Port 3528: use nvidia graphics automatically on laptops with optimus

* Force dedicated AMD Card for switchable Graphics

* Ran clang-format

nvflinger: Call MicroProfileFlip on NVFlinger::Compose.

GPU: Add support for the DXT23 and DXT45 compressed texture formats.

GPU: Implemented the B5G6R5 format.

* gl_shader_gen: Support vertical/horizontal viewport flipping.

* fixup! gl_shader_gen: Support vertical/horizontal viewport flipping.

GPU: Fixed the incorrect component order in ABGR8 textures.

For now only the UNORM type is supported.

GPU: Support non-tiled textures and configurable block height.

TODO: The way we handle cached formats must change, framebuffer and texture formats are too different to keep them in the same place.

Clarifies the yuzu cannot play commercial games to any reasonable extent, rather than not at all.

Misc gpu improvements

Shader decompiler changes part 2

renderer_opengl: Implement BlendEquation and BlendFunc.