Add a check for missing modules or dependencies

Description of the need

Since 7.50 Drupal has included a check that alerts you if there is a missing file, module or dependencies. We recently saw in a Forum post that, if you update modules by pushing them through git instead of using the UI, and if the update does not require a database update, you may not catch a missing dependency. For example, recently, Rules started depending on Entity Tokens. That update did not require any database update. So if you updated Rules by pushing it, or manually moving its folder into the modules folder, you may not be aware of the missing dependency, unless you either run update.php (which will alert you right away) or you install a new module via the UI (which performs that check).

See Drupal's record change and issue 1081266. This issue was mentioned in the Backdrop queue https://github.com/backdrop/backdrop-issues/issues/2013, and its checkbox was marked as complete, but in fact this feature was never ported to Backdrop.

Proposed solution

Crossport D7 issue 1081266