Add more layout constraints to tokenizer CSS to prevent layout issues with Chinese glyphs in Firefox 73

Summary:
Fixes T13495. See that task for details.

Tokenizer tokens which contain Chinese glyphs are slightly taller than normal tokens in Firefox 73, and at some non-100% zoom levels in other browsers.

This cauess the tokenizer list to layout and line break oddly.

Fix this by clamping tokenizer sizes more aggressively. Specifying a max-height means they can no longer line wrap, so this also requires more specification of overflow behavior.

Test Plan:
Before:

{F7216435}

After:

{F7216439}

Maniphest Tasks: T13495

Differential Revision: https://secure.phabricator.com/D21026