Writing InstrumentationModule line by line

[mateuszrzeszutek]

Is your feature request related to a problem? Please describe.
InstrumentationModule is getting increasingly complicated (which is mostly my fault 😂 ) and we don't really have a good doc/resource on how to implement one correctly. Sure, there's Javadoc but you have to piece everything together by yourself.

I thought that it would be useful for contributors to have a single doc that explains all conventions and gotchas that you have to know when implementing an InstrumentationModule: module names, injecting helpers, library instrumentation, how to avoid VerifyErrors and so on.