firestore:delete should notify the user of the current project

[davidbrenner]

[REQUIRED] Environment info

 % firebase --version
9.11.0

firebase-tools:

Platform: linux

[REQUIRED] Test case

% firebase firestore:delete -r users  
? You are about to delete all documents in the collection at users and all of their subcollections. Are you sure? (y/N)

[REQUIRED] Steps to reproduce

% firebase firestore:delete -r users  
? You are about to delete all documents in the collection at users and all of their subcollections. Are you sure? (y/N)

[REQUIRED] Expected behavior

firestore:delete should tell the user in the confirmation the project from which they are deleting documents. This was specifically problematic for me when I used the command on Google Cloud Console's Shell. The shell prints the current gcloud project, but firebase-tools ignores that. A simple confirmation message would have saved me a lot of headache. I put together a PR that I will be submitting momentarily that includes my proposed fix:

% firebase firestore:delete -r users  
? You are about to delete all documents in the collection at users and all of their subcollections for **project-name**. Are you sure? (y/N)

[REQUIRED] Actual behavior

% firebase firestore:delete -r users  
? You are about to delete all documents in the collection at users and all of their subcollections. Are you sure? (y/N)