Per the Stable Interface Policy, PHP interfaces should not be
directly implemented by extensions, unless they are marked to be safe
for that purpose.
Bug: T247862
Change-Id: Idd5783b70fc00c03d57f5b1a887f0e47c4d7b146
This follows-up d83fcce5cb, which did something similar for
includes/profiler/.
* Ensure presence of license header.
* Merge any file-level descriptions with the class block,
where it gets seen in generated docs about that class.
* Add any missing `@ingroup` tags to class blocks.
* Remove remaining `@ingroup` from file blocks.
These clutter the Doxygen pages with duplicate entries.
* Fix some misspelled words from 61e0908fa2 and f136c2953c.
Change-Id: I5d21ec159766b799ba519da951d4f0716bae5f9f
