cli: add jj hide as an alias for jj abandon

I keep explaining the functionality as hiding the commit, so it seems
that `jj hide` is a natural name for it. Let's start by adding it as
an alias. My only hesitation with making `hide` the real command name
and `abandon` an alias that we start phasing out is that it feels more
natural to `abandon` the working copy in order to start working on a
new change than it does to `hide` it.

src/commands.rs

@@ -1407,6 +1407,7 @@ struct DuplicateArgs {
 /// similar to `jj restore`; the difference is that `jj abandon` gives you a new
 /// change, while `jj restore` updates the existing change.
 #[derive(clap::Args, Clone, Debug)]
+#[clap(visible_alias = "hide")]
 struct AbandonArgs {
     /// The revision(s) to abandon
     #[clap(default_value = "@")]