Add a :version command to GHCi

Summary

Add a :version command to GHCi. This would show either the same as ghc --version, or the (beginning of the) first output line of GHCi, which is e.g. "GHCi, version 9.11.20240322: https://www.haskell.org/ghc/ :? for help".

This command would especially make sense when used while GHCi is started in a quiet mode (e.g. with -v0), where such information would not be displayed at startup.

(I guess it would also make sense in the case of a Machine accessible interface to GHCi #15461, so a controlling client could query such information.)