Add a restore command for WP-CLI

[benoitchantre]

Is your feature request related to a problem? Please describe.
When there are a lot of images to restore, this is a tedious process using the media library, even with the bulk action.

Describe the solution you'd like
It would be very useful to have a restore subcommand to handle that task efficiently.

Additional context
A restore command is needed, because when you change the compression settings from smart to lossless, a lossless compression is applied on lossy images instead of restoring the original file instead before apply the lossless compression.