Make lookupSymbolInformation() a private API on CelerityResourceMap

Summary: Ref T4222. Same deal as D7867, but for this other super nebulous "return a blob of stuff" method.

Test Plan: Regenerated map, browsed around, etc.

Reviewers: btrahan, hach-que

Reviewed By: hach-que

CC: aran

Maniphest Tasks: T4222

Differential Revision: https://secure.phabricator.com/D7868