This is 2nd attempt of I8df992a6851021903478972601a9a5c9424b100c.

The main purpose of this CL is expanding FontLanguage to be able to
save full script tag. Previously, FontLangauge kept only limited script
tags. With this CL, FontLanguage keeps all script tags.

This CL contains the following changes:
- FontLanguage changes:
-- Moved to private directory not to be instantiated outside of Minikin.
-- Removed bool(), bits(), FontLanguage(uint32_t) methods which are no
   longer used.
-- Change the FontLanguage internal data structure.
-- Introduces script match logic.

- FontLanguages changes:
-- Moved to private directory not to be instantiated outside of Minikin.
-- This is now std::vector<FontLanguage>

- FontLanguageListCache changes:
-- Now FontLanguageListCache::getId through
   FontStyle::registerLanguageList is the only way to instantiate the
   FontLanguage.
-- Normalize input to be BCP47 compliant identifier by ICU.

Bug: 26168983
Change-Id: I431b3f361a7635497c05b85e8ecbeb48d9aef63e