Rename all?, any? and empty? (#6464)

Rename `all?`, `any?` and `empty?` to `all`, `any` and `is-empty` for sake of simplicity and consistency.

- More understandable for newcomers, that these commands are no special to others.
- `?` syntax did not really aprove readability. For me it made it worse.
- We can reserve `?` syntax for any other nushell feature.

crates/nu-command/tests/commands/zip.rs

@@ -8,7 +8,7 @@ export def expect [
     --to-eq,
     right
 ] {
-    $left | zip $right | all? {|row|
+    $left | zip $right | all {|row|
         $row.name.0 == $row.name.1 && $row.commits.0 == $row.commits.1
     }
 }