Child process and `utbot-instrumentation` module design documentation

[sergeypospelov]

Description

Add a documentation on the child process working pipeline and whole utbot-instrumentation module, as well as on a UtExecutionInstrumentation class.

Maybe we could create a draft page and add more aspects to it over time.

Details

What to include:

• The base concept
• API
  • Passing paths to user and dependency classes
• Inter-process communication: RD
• Kryo and serializing
• Pipeline of loading a new class into JVM
• Logging and errors file
• A simple usage example
• UtExecutionInstrumentation
  • API
  • MockValueConstructor
    • Mocks (Mockito, our own mocks)
  • Timeouts and ThreadBasedExecutor
  • UtModelConstructor
• How to create your own instrumentations