Refactor generator to use configuration to load sources and filters

[C-SELLERS]

This stubs generator is very powerful specifically in its parsing of source files and generation of stubs. However, in its current implementation the driving program is limited in that it is set to support specific repos (QC/Lean repo, and dotnet/Runtime repo). Where search patterns and filters are hardcoded into the program.

I believe with some modification to the driving program we could easily support a configurable generic approach to loading in repos (and accompanying filters/search patterns) to be added to the stubs.

This isn't critical to its functionality that it serves for QC but it would open up the applications for this software significantly.

In example, we recently merged a workaround for Lean stubs generation where I load in additional DataSource repos inside of the Lean repo I pass to the generator. This added all of our DataSource sets the to stubs. This is great, but it was a hacky workaround that required a PR on both LEAN and this Repo to hardcode the addition of those repos and the filtering.

See this for that example