general: Remove unused boost inclusions where applicable

configure_system: Fix compiler warning

Cleans up unused includes and trims off some dependencies on externals.

* get rid of boost::optional

* Remove optional references

* Use std::reference_wrapper for optional references

* Fix clang format

* Fix clang format part 2

* Adressed feedback

* Fix clang format and MacOS build

 hle_ipc: Make GetDomainMessageHeader return a regular pointer

Gets rid of the need to call the getter and then check for null.

Nothing requires the shared owner ship here, so we can just return a
plain pointer.

core: Add missing const variants of getters for the System class

Implemented Mipmaps

time_stretch: Switch to values of Citra

video_core: Move OpenGL specific utils to its renderer

renderer_opengl: Enable alpha channel for DXT1 texture format

renderer_opengl: Correct bpp value for ASTC_2D_8X5_SRGB

Many of the Current<Thing> getters (as well as a few others) were
missing const qualified variants, which makes it a pain to retrieve
certain things from const qualified references to System.

renderer_opengl: Correct bpp value for ASTC_2D_8X5

Improved Shader accuracy on Vertex and Geometry Shaders.

Revert "Update MACOSX_DEPLOYMENT_TARGET to 10.14"

svc: Implement svcGetInfo command 0xF0000002

Update MACOSX_DEPLOYMENT_TARGET to 10.14

* remove unnecessary if-statements

* Addressed feedback

service/filesystem: Implemented DeleteDirectory & DeleteDirectoryRecursive

loader/nsp: Move secondary loader initialization to constructor

Implement sRGB support