Implement query energy estimation

[joshua-spacetime]

Requirements:

• Initial subscription and ad hoc queries whose estimated energy consumption exceeds limit will fail before being executed
• The energy limit should be configurable at runtime
• We should have separate limits for owner and non-owner identities

Non-requirements:

• Energy estimation does not have to be absolutely accurate, but it should be relatively accurate
  • That is if energy(A) >= energy(B), then estimate(A) >= estimate(B)