Simplify directory structure and cleanup old entrypoints

The old RIG entrypoint was removed since the hardware is not there anymore.
The base-groundstation entrypoint was removed as well since it was non-functional and couldn't even be built via CMake.

The directory structure has been consolidated under the src directory, removing unnecessary folder nesting which might be confusing for those new to the repo.
The scripts folder has been brought out of the src directory as it doesn't contain sources that are compiled by the usual build system invocations.

Some big files have been removed (if unused) or renamed to be excluded from clang-format, which now takes ~1s instead of >20s.