Update the `JSONLint` API

Summary:
Update the [[https://github.com/Seldaek/jsonlint/ | JSONLint]] external to more closely resemble the upstream. {D9623} patched the library to return an `array` instead of `stdClass`, however this functionality now exists upstream as an optional mode (see [[https://github.com/Seldaek/jsonlint/commit/351e4350171d9c3af292cfb524dd83badb283e62 | 351e4350171d9c3af292cfb524dd83badb283e62]]).

I basically copied the external verbatim and then applied a sequence of patches (the initial patches required for D9622, plus D9633).

Test Plan: Ran unit tests.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10433