Configurable idempotency check in the playground

[torhovland]

Is your feature request related to a problem? Please describe.
The user should be able to choose whether or not to run idempotency check in the playground.

This is useful when debugging why the idempotency check fails.

Describe the solution you'd like
A simple checkbox for disabling idempotency check.

Describe alternatives you've considered
The alternative is to always have idempotency check enabled or disabled. None of which are ideal.

Additional context
See https://ormolu-live.tweag.io for inspiration.