refactor(github): Uniform names for github datasource types (#17701)

...dules/datasource/github-releases/cache/cache-base.spec.ts

lib/modules/datasource/github-releases/cache/cache-base.ts

lib/modules/datasource/github-releases/cache/index.spec.ts

lib/modules/datasource/github-releases/cache/index.ts

lib/modules/datasource/github-releases/digest.spec.ts

lib/modules/datasource/github-releases/index.ts

lib/modules/datasource/github-releases/test/index.ts

lib/modules/datasource/github-tags/cache.spec.ts

lib/modules/datasource/github-tags/cache.ts

lib/modules/datasource/github-tags/index.ts

lib/modules/datasource/hermit/index.ts

lib/util/github/types.ts

lib/workers/repository/update/pr/changelog/github/index.ts