Add & use PhoneMetadata.metadata_for_region accessor
Add & use PhoneMetadata.metadata_for_nongeo_region accessor
Use accessors in metadata_for_region_or_calling_code
Add on-demand loader mechanism for metadata
Use common REGION_CODE_FOR_NON_GEO_ENTITY
Confirm use of int for nongeo key type
Move tests to use accessors
Test metadata needs to replace loaders too
Generate on-demand loaders for metadata
Regenerated metadata masters, using on-demand loaders
Underscore-prefix internal class variables.
Add method to force immediate load of metadata