Search Symbols by Repository, not Project

Summary:
Fixes T7977.

• Move Indexed Languages and See Symbols From config to Repository
• Make symbol search skip projects

This also makes the default languages to Everything instead of Nothing.

Test Plan:

• Browse files, click symbols.
• Use quick search to find symbols
• Browse revision, click symbols

Reviewers: joshuaspence, epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T7977

Differential Revision: https://secure.phabricator.com/D12687