Add new fonts.xml

This adds a new configration file for fonts with several more features,
most notably the ability to specify numeric weights for fonts in a
family, and specify aliases for weights. This will help help choose an
appropriate font for a "bold" weight request, rather than just applying
auto-bolding.

Bug: 14538154
Change-Id: Ib4d54d66a0c68b7d46e665d7cd94e97b72468e95