Add docs on Interprocess debugging

[olganaumenko]

Description

We have split the UnitTestBot machinery into three processes. This approach has improved UnitTestBot capabilities but also complicated the debugging flow.
We need to document this and keep the docs up to date.

• Create the docs/contributing folder in the repo
• Add the document on debugging the IDE process and the Engine process
• Update the synchronizer.measureExecutionForTermination() method name
• Add illustrations
• Add info on debugging the Concrete execution process
• Specify info on adding more ports and other hacks