Add font descriptions for six more scripts to fonts.xml

Font data for Phags-pa, Runic, Samaritan, and Tagalog are added, as
well as two new styles for Syriac (Estrangela was already included,
Eastern and Western are added).

Bug: 29535549
Bug: 32046261
Test: manual (new characters are now displayed) and 'make fontchain_lint'
Change-Id: Iad08286392850caf92e374818bd29d06b6a87e52