Remove ApiBase::createContext() (deprecated since 1.19)

Change-Id: Iee20e1c5e5b83b5b43303bde7e524b95b74eb62b
Add parser test for "extra interlanguage links".

This support was added in https://gerrit.wikimedia.org/r/111390
but no parser tests were added at that time.

Bug: 32189
Change-Id: I299ce844919b3f20b3ce116adf64b37dd95325d0
Merge "Add parser test for "extra interlanguage links"."
Merge "Remove ApiBase::createContext() (deprecated since 1.19)"