Investigate updating the re2 matcher to use an atom length of 2

[masklinn]

The uap workload seems to greatly benefit from using pair atoms cf ua-parser/uap-rust#31

[masklinn]

Nota: looks like only the devices parser should be updated to an atom length of 2, per ua-parser/uap-rust#32.

[masklinn]

Whelp, checking the Python re2 API re2.Filter takes no parameters and calls _re2.Filter which also takes no parameters, and simply default-constructs a FilteredRE2. So... regex will be pulling ahead hard.