Speed up builds for both AUI and AUI-based applications

As the project grows, the build times too. Due to my insane love for template metaprogramming, it contributes to build times, too. A cpp file that includes AForEachUI.h compiles considerably slower.

We need to research additional ways to improve compilation speeds. There are ways I know:

- precompiled headers
- cmake unity builds
- aui has many ODR violations, i.e, `static constexpr auto LOG_TAG`
- clang has build time profiling flag; should recognize and fix time consuming headers

Start by profiling compilation of a C++ file that includes AForEachUI.h with Clang's build-time profiling flag. Compare precompiled headers and CMake unity builds, while checking the noted ODR violations such as static constexpr auto LOG_TAG. Done means a measured compilation-speed improvement for AUI and AUI-based applications without introducing those violations.

Written by the indexing model from the issue text.