deprecate(libraries): undeprecate the elgg_register/load_library functions

This reverts commit 190b69216e889274621b3ca15b5055c605b1067c.
chore(libraries): update library loading functions to use config service
Merge pull request #7563 from mrclay/undeprecate_libs

Undeprecate and update the elgg_load/register_library functions