Write a cleaner/more general version of grailbio/bazel-compilation-database

Created by: shrouxm

Ideally users should just be able to input:

• which bazel outputs need to actually be built to compile the code (headers, generated code)
• a bazel expression for which targets we need to analyze the dependency graph of and get a compile_commands.json.

We should also provide good general defaults for these values. grailbio/bazel-compilation-database for example uses a hardcoded and very short list of possible C++ file extensions to figure out which targets to analyze.