Fix an issue where "Browse > Select" did not work for dynamic tokenizers

Summary:
Ref T4100. In Herald, using the browse dialog to select a result didn't work because we'd add the token with no name value. Other things would render it elsewhere, but it would eventaully be discarded.

Instead, add it with a name value.

Test Plan: Edited a Herald rule and used Browse > Select to add a token. Saved rule. Saw token persist.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4100

Differential Revision: https://secure.phabricator.com/D12529