Prevent screen and action files to be loaded more than once into Components class

[imath]

I've noticed bp-component/actions/anyfile.php or bp-component/screens/anyfile.php can be loaded more than once now we've moved to BP Rewrites. The test I made was clicking on the "Add Friend" button from the Members directory, it ended up with a fatal as the bp-members/screens/directory.php was loaded more than once, and as a result the bp_members_screen_index() function defined more than once.

To avoid potential issues, we should use require_once instead of require in all Components class late_includes() methods.

To avoid potential issues, use require_once instead of require in all Components class late_includes() methods.

Trac ticket: ​https://buddypress.trac.wordpress.org/ticket/8910

[imath]

In 13495:

Prevent potential issues with late_includes() in Component classes

Use require_once instead of require to load action & screen files.

See #4954
Fixes #8910
Closes ​https://github.com/buddypress/buddypress/pull/112