* Generate RegionCode constants for testing.
This generates the RegionCode class that contains string constants for testing using the build tools.
Context: b/237181793
* Fix typo
* Use plain strings for region codes not in the metadata.
* Apply code review suggestions
* Rewrite ClassWriter with Builder pattern and add javadoc support.
* Use setJavadoc instead of accumulating.
* Update ShortNumberInfo test regarding example number change for region AM. Unlike PhoneNumberUtilTest, ShortNumberInfoTest uses real metadata for unit testing.
* Changing the region as Travis tests do not pass with old short metadata of AM
* Making same changes in CPP and JS