R1:72cb3d3c8490

Limit the damage that degenerate project name typeahead queries can cause

Summary:
See PHI47. When users copy/paste a wall of text into a project tokenizer, we can end up performing a very large number of JOINs.

These JOINs seem okay locally and on `secure`, but the install in PHI47 reports hitting issues.

Since these queries are almost certainly illegitimate (I think no one uses 5+ words to find a project), just limit the search to the 5 longest tokens.

Note that typing 6 tokens will still almost…