Add an ability to run the EXPLAIN command without execution

Goal

• Add command for running explain without execution

TODO / How to implement

Running explain without execution (e.g., useful for hypothetical indexes):

plan SELECT * FROM hypo WHERE id = 1;

Alternative naming:

• explain-noexec SELECT * FROM hypo WHERE id = 1;
• explain-only SELECT * FROM hypo WHERE id = 1;
• hypoexec SELECT * FROM hypo WHERE id = 1;
• estimate SELECT * FROM hypo WHERE id = 1;

Acceptance criteria

As a user I can run EXPLAIN without execution