feat(spec,rest): the authored label is the default locale's text — ResolveOptions.defaultLocale skips the fallback chain, and a chain-less caller no longer falls to a literal en (#15711)

feat(spec,rest): the authored label is the default locale's text — ResolveOptions.defaultLocale skips the fallback chain, and a chain-less caller no longer falls to a literal en (#15711) #1715