R1:96fe8c0b83cf

Implement basic ngram search for Owners Package names

Summary:
Ref T9979. This uses ngrams (specifically, trigrams) to build a reasonably efficient index for substring matching. Specifically, for a package like "Example", with ID 123, we store rows like this:

```
< ex, 123>
<exa, 123>
<xam, 123>
<amp, 123>
<mpl, 123>
<ple, 123>
<le , 123>
```

When the user searches for `exam`, we join this table for packages with tokens `exa` and `xam`. MySQL can do this a lot more efficiently than it can process a…