Identify the version of a collation from ICU in Postgres

Postgres 10 and later incorporates the International Components for Unicode (ICU) library for text-handling and other internationalization issues. Changes happen to human languages, such as sorting rules evolving. Therefore collation definitions are versioned in ICU. ➥ How can I identify the version number of a collation? I know Postgres will report version number as part of a collation version mismatch error message. Is there a way to proactively query for the version rather than wait for an error message?