Provide a generic extract (and compress) commands in base

[mojca (Mojca Miklavec)]

It would be extremely useful to introduce a command like

file_extract foo.tar.xz

in the core, so that ports could even "manually" extract (or compress) additional files when needed.

At the moment MacPorts supports fetching distfiles from different mirrors, but it doesn't support extracting different filetypes, so all the "hard work" of extracting the proper file has to be repeated manually in the Portfile. It might also be useful to be able to extract additional tarballs when fetching from git/svn, so the command would be helpful in many different context.

MacPorts could also have the ability to automatically use different extract methods based on filenames (that is: when file extension is specified; use_xz would then only influence the default type that could theoretically be overwritten).

(The other nice-to-have functionality would be the ability to create (reproducible) tarballs on demand as requested in #50896.)