remove the deprecated register command (#13297)

# Description

This PR removes the `register` command which has been
[deprecated](https://www.nushell.sh/blog/2024-04-30-nushell_0_93_0.html#register-toc)
in favor of [`plugin
add`](https://www.nushell.sh/blog/2024-04-30-nushell_0_93_0.html#redesigned-plugin-management-commands-toc)

# User-Facing Changes

`register` is no longer available

crates/nu-cmd-plugin/src/commands/mod.rs

@@ -1,5 +1,3 @@
 mod plugin;
-mod register;
 
 pub use plugin::*;
-pub use register::Register;

crates/nu-cmd-plugin/src/commands/plugin/stop.rs

@@ -72,7 +72,7 @@ impl Command for PluginStop {
                 error: format!("Failed to stop the `{}` plugin", name.item),
                 msg: "couldn't find a plugin with this name".into(),
                 span: Some(name.span),
-                help: Some("you may need to `register` the plugin first".into()),
+                help: Some("you may need to `plugin add` the plugin first".into()),
                 inner: vec![],
             })
         }

crates/nu-cmd-plugin/src/commands/register.rs

@@ -1,80 +0,0 @@
-use nu_engine::command_prelude::*;
-use nu_protocol::engine::CommandType;
-
-#[derive(Clone)]
-pub struct Register;
-
-impl Command for Register {
-    fn name(&self) -> &str {
-        "register"
-    }
-
-    fn usage(&self) -> &str {
-        "Register a plugin."
-    }
-
-    fn signature(&self) -> nu_protocol::Signature {
-        Signature::build("register")
-            .input_output_types(vec![(Type::Nothing, Type::Nothing)])
-            .required(
-                "plugin",
-                SyntaxShape::Filepath,
-                "Path of executable for plugin.",
-            )
-            .optional(
-                "signature",
-                SyntaxShape::Any,
-                "Block with signature description as json object.",
-            )
-            .named(
-                "shell",
-                SyntaxShape::Filepath,
-                "path of shell used to run plugin (cmd, sh, python, etc)",
-                Some('s'),
-            )
-            .category(Category::Plugin)
-    }
-
-    fn extra_usage(&self) -> &str {
-        r#"
-Deprecated in favor of `plugin add` and `plugin use`.
-
-This command is a parser keyword. For details, check:
-  https://www.nushell.sh/book/thinking_in_nu.html
-"#
-        .trim()
-    }
-
-    fn search_terms(&self) -> Vec<&str> {
-        vec!["add"]
-    }
-
-    fn command_type(&self) -> CommandType {
-        CommandType::Keyword
-    }
-
-    fn run(
-        &self,
-        _engine_state: &EngineState,
-        _stack: &mut Stack,
-        _call: &Call,
-        _input: PipelineData,
-    ) -> Result<PipelineData, ShellError> {
-        Ok(PipelineData::empty())
-    }
-
-    fn examples(&self) -> Vec<Example> {
-        vec![
-            Example {
-                description: "Register `nu_plugin_query` plugin from ~/.cargo/bin/ dir",
-                example: r#"register ~/.cargo/bin/nu_plugin_query"#,
-                result: None,
-            },
-            Example {
-                description: "Register `nu_plugin_query` plugin from `nu -c` (writes/updates $nu.plugin-path)",
-                example: r#"let plugin = ((which nu).path.0 | path dirname | path join 'nu_plugin_query'); nu -c $'register ($plugin); version'"#,
-                result: None,
-            },
-        ]
-    }
-}

crates/nu-cmd-plugin/src/default_context.rs

@@ -18,7 +18,6 @@ pub fn add_plugin_command_context(mut engine_state: EngineState) -> EngineState
             PluginRm,
             PluginStop,
             PluginUse,
-            Register,
         );
 
         working_set.render()