Add Belarusian and Latin patterns and update German

1. Add Belarusian and Latin patterns (Liturgical Latin patterns are
not built, since there is no standard BCP 47 tag yet).

2. Switch the upstream for German patterns back to tex-hyphen and
update the data files.

3. Update Church Slavonic patterns to latest upstream data.

4. Update the various README files to refer to new upstream and its
latest version.

Bug: 65626527
Test: mmm -j external/hyphenation-patterns
Change-Id: I3a58a78f70ec15e586621aee1743d096c6289c71