Support HypoPG

Goal

Add a possibility to try indexes without its creation using an extended Database Lab Docker image.

TODO / How to implement

• do not change the current explain syntax
• show info in the main message if hypo index is used:
  • check hypo indexes which have been created
  • check indexes used for the query
  • print plan without an execution to the main message in case the matching
• describe in the docs how to use:
  • create extension
  • create hypo indexes
  • use explain

Acceptance criteria