Add a command to run a query in 'dry run' mode

[dan-nom]

Show success or failure messages through the showInformationMessage toasts.

[googlebot]

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[dan-nom]

I signed it!

[googlebot]

CLAs look good, thanks!

[dan-nom]

Thanks for the prompt review. PTAL.

[elithrar]

Merged - thanks @dan-nom!