Refactor FeaturesInstallStorage

The purpose of FeaturesInstallStorage is to mimic the core ExtensionInstallStorage except it reads configuration from modules that are not installed.

In the latest few D8 betas, the ExtensionInstallStorage::getAllFolders() function has changed extensively. In fact, it now performs a full module scan, so it *almost* handles uninstalled modules.

The patch in #2497155: getComponentNames must be of the type array didn't correctly refactor this when the getComponentNames() function changed it's API. After the patch it is functional, however, it is doing a bunch of duplicate code since the protected getAllModules() that was added is doing the same listing scan that is already in the core getAllFolders().

We can greatly simplify this service now by removing getAllModules() and just using the scan listing already being executed.

Here is the patch to -dev to get this back to something that more closely matches the core service.

There are only 2 changes to core, marked with the CHANGED text:

1) Add directories for additional profiles specified in bundles
2) Use ALL modules from scan instead of just enabled modules.