Add command line options to change passwords

[inetic]

The "main" secret is really the share token, so if the user loses their read or write passwords, they should still be able to change them if they have the share token. We have functions for this:

https://github.com/equalitie/ouisync/blob/3c0a514cb615f5c5e0f1568115654a366ffd857e/lib/src/repository/mod.rs#L238-L322

But there's currently no way to use it from the command line.

[IvanaBlzvc]

https://redmine.equalit.ie/issues/31629