[feature] Query Explain Plan

[TuSKan]

A feature to return plans of a Query, without executing it.

Analyzes the performance of a specified SOQL query, report, or list view.

sf query explain

[k-capehart]

@TuSKan This is a cool idea to add. Can you talk a bit about the use cases to using this in a client app?

[TuSKan]

Thank you for being open to discuss this PR.
My use case for this feature is to have a estimation of number of records and very costly queries before effectively request a query, to avoid or warning long time duration API calls.

[k-capehart]

Thanks for the explanation. Merging this into a feature branch now.