Document missing Lock::Async methods
Document missing Lock::Async methods

This documents Lock::Async.protect-or-queue-on-recursion and
Lock::Async.with-lock-hidden-from-recursion-check.

Fixes #2785

perl6/doc,perl6/doc,MasterDuke17/doc,tbrowder/doc,tbrowder/doc,perl6/doc,perl6/doc,MasterDuke17/doc,MasterDuke17/doc,perl6/doc,tbrowder/doc,MasterDuke17/doc,tbrowder/doc