Tokenize datasource indexes on "(" and ")"

Summary:
Fixes T11955. Milestone names are currently tokenizing and indexing awkwardly. For example, "A (B C D)" becomes the tokens "A", "(B", "C" and "D)".

The token "(B" can't be searched for since "(" is tokenized on the client.

Instead, tokenize "A (B C D)" into "A", "B", "C", "D".

Test Plan:

• Added unit tests.
• Used bin/search index --type project --force to reindex.
• Searched for "A", "B", "C", "D", etc., for real examples.
• Now, found milestones more consistently.
• Also serached for viewer(), members(), etc.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11955

Differential Revision: https://secure.phabricator.com/D17012