Add missing variable names to PHPDoc @param of methods

Summary:
Add variable names ($varname in @param type $varname explanation) to PHPDoc method headers, for fun and profit.

Closes T15923

Test Plan:

• Read the method signatures and their corresponding PHPDoc headers at your fireplace
• Still run ./bin/diviner generate without explosions (though it is very lenient anyway?)

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15923

Differential Revision: https://we.phorge.it/D25794