Function to automatically Precompile all concrete method signatures

[NHDaly]

:) We talked about this in person at JuliaCon; filing an issue for it.

It would be awesome if there was functionality to automatically precompile all concretely-typed method signatures in a module. Something like:

PrecompileTools.precompile_static_signatures()

This could reflect over the module and find all reachable methods that have concrete signatures and include them in what's precompiled. For some applications (like RAI's) this could get pretty significant precompile coverage with very little work.

We may want to provide an option (default to true?) to control whether or we also pick up methods extending functions owned by package dependencies. To support that, we'll need to vendor in the kind of analysis that MethodAnalysis.jl does to find those methods.