Set to reedline main branch for development cycle (#5249)

Changes to reedline since `v0.4.0`:

- vi normal mode `I` for inserting at line beginning
- `InsertNewline` edit command that can be bound to `Alt-Enter` if
desired to have line breaks without relying on the `Validator`
- `ClearScreen` will directly clear the visible screen. `Signal::CtrlL` has been
removed.
- `ClearScrollback` will clear the screen and scrollback. Can be used to
mimic macOS `Cmd-K` screen clearing. Helps with #5089

crates/nu-cli/src/reedline_config.rs

@@ -814,6 +814,7 @@ fn event_from_record(
         "none" => ReedlineEvent::None,
         "actionhandler" => ReedlineEvent::ActionHandler,
         "clearscreen" => ReedlineEvent::ClearScreen,
+        "clearscrollback" => ReedlineEvent::ClearScrollback,
         "historyhintcomplete" => ReedlineEvent::HistoryHintComplete,
         "historyhintwordcomplete" => ReedlineEvent::HistoryHintWordComplete,
         "ctrld" => ReedlineEvent::CtrlD,
@@ -881,6 +882,7 @@ fn edit_from_record(
             let value = extract_value("value", cols, vals, span)?;
             EditCommand::InsertString(value.into_string("", config))
         }
+        "insertnewline" => EditCommand::InsertNewline,
         "backspace" => EditCommand::Backspace,
         "delete" => EditCommand::Delete,
         "backspaceword" => EditCommand::BackspaceWord,

crates/nu-cli/src/repl.rs

@@ -314,9 +314,6 @@ pub fn evaluate_repl(
                 println!();
                 break;
             }
-            Ok(Signal::CtrlL) => {
-                line_editor.clear_screen().into_diagnostic()?;
-            }
             Err(err) => {
                 let message = err.to_string();
                 if !message.contains("duration") {