Improvement: Package dependencies for lambda

[strcrzy]

We already have code to package and deploy third party libraries, but it might be cool to have SA package its own dependencies (from requirements.txt) into the deployment archive as well. #40 introduced a new lambda dependency, and other revisions likely will too.

We could track these in third_party_libs in variables.json but IMO those should just be the dependencies of the rules themselves rather than their underlying infrastructure.

[ryandeivert]

this is actually complete and we have these in the packaging logic