investigate clang-scan-deps tool for the tu_collector

[gyorb]

@Xazax-hun mentioned the clang-scan-deps tool in another PR comment #2765.

The first version is available since clang-9 it can be found here llvm-project/clang/tools/clang-scan-deps/ and can be built with the make clang-scan-deps command.
clang-scan-deps provides similar feature what is done by the tu_collector, to get the source files
in a translation unit, it might be worth to investigate the features.
There is a conference video about it 2019 EuroLLVM Developers’ Meeting: clang-scan-deps: A. Lorenz & M. "Spencer Fast dependency ...”

It might be faster than the current preprocessor based solution.
The used compile command database should contain the implicit include paths too to find the right files. The current log phase does not add the implicit include paths to the compile command database it is only done before the analyzers are started.