Instrumentation stage prior to App2App

Currently there are 4 main instrumentation stages:
- Application-to-application transformations
- Application code analysis
- Instrumentation insertion
- Instrumentation-to-instrumentation transformations

This issue suggests an additional instrumentation stage to be triggered firstly, prior to the app2app.

There are cases where app transformations depend on some analysis of the original application code. Currently, one requires performing this analysis along with transformations by using the same callback. It would be great if we can have an additional callback to an event prior to app transformations in order to separate concerns. Users won't be able to make any transformations via the callback.

Consequently, we will be left with:
- **Original Application code analysis**
- Application-to-application transformations
- Application code analysis
- Instrumentation insertion
- Instrumentation-to-instrumentation transformations