Add more emoji-related tests

1. Check that dual-use text/emoji character that default to text
style are available in a font before the emoji font. (Exceptions are
Unicode 7.0 characters that Noto Symbols doesn't support yet and four
odd characters that should be added to the Noto Symbols subset.)

2. Remove previous workaround for default emoji-style characters that
were in the Noto CJK fonts, since they are now subsetted out from
Noto CJK.

Bug: 26113320
Bug: 26187231
Change-Id: Ib9ea2f4f7e6ca0cd8d291f1dc3d7ee5053d4928e