Allow instrumenting calls to libraries

[dividedmind]

It can be useful to allow the user to record arbitrary calls to external libraries (standard or third party), with the choice of instrumenting them entirely or only at entry points ("shallow mode"). While instrumenting third party libraries entirely is currently possible with the right configuration (eg. packages: { path: node_modules/some_library }) it's not possible for standard libraries and shallow mode is likewise not supported.

Appmap.yml packages should support entries like module: some-library that also accept shallow: true.