Make bin/storage upgrade and bin/storage adjust emit detailed messages if the user has no access to databases

Summary:
Ref T10195. Distinguish between "database does not exist" and "database exists, you just don't have permission to access it".

We can't easily get this information out of INFORMATION_SCHEMA but can just SHOW TABLES IN ... every database that looks like it's missing and then look at the error code.

Test Plan:

• Created a user limited with limited access.
• Ran bin/storage adjust.
• Got hopefully more helpful messages about access problems, instead of "Missing" errors.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10195

Differential Revision: https://secure.phabricator.com/D15079