Better generic errors for plugins (and perhaps scripts) (#12236)

# Description
This makes `LabeledError` much more capable of representing close to
everything a `miette::Diagnostic` can, including `ShellError`, and
allows plugins to generate multiple error spans, codes, help, etc.

`LabeledError` is now embeddable within `ShellError` as a transparent
variant.

This could also be used to improve `error make` and `try/catch` to
reflect `LabeledError` exactly in the future.

Also cleaned up some errors in existing plugins.

# User-Facing Changes
Breaking change for plugins. Nicer errors for users.

crates/nu_plugin_custom_values/src/drop_check.rs

@@ -1,6 +1,7 @@
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
 use nu_protocol::{
-    record, Category, CustomValue, PluginSignature, ShellError, Span, SyntaxShape, Value,
+    record, Category, CustomValue, LabeledError, PluginSignature, ShellError, Span, SyntaxShape,
+    Value,
 };
 use serde::{Deserialize, Serialize};
 

crates/nu_plugin_custom_values/src/generate.rs

@@ -1,7 +1,7 @@
 use crate::{cool_custom_value::CoolCustomValue, CustomValuePlugin};
 
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginExample, PluginSignature, Span, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{Category, LabeledError, PluginExample, PluginSignature, Span, Value};
 
 pub struct Generate;
 

crates/nu_plugin_custom_values/src/generate2.rs

@@ -1,7 +1,9 @@
 use crate::{second_custom_value::SecondCustomValue, CustomValuePlugin};
 
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginExample, PluginSignature, Span, SyntaxShape, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{
+    Category, LabeledError, PluginExample, PluginSignature, Span, SyntaxShape, Value,
+};
 
 pub struct Generate2;
 

crates/nu_plugin_custom_values/src/main.rs

@@ -1,6 +1,4 @@
-use nu_plugin::{
-    serve_plugin, EngineInterface, LabeledError, MsgPackSerializer, Plugin, PluginCommand,
-};
+use nu_plugin::{serve_plugin, EngineInterface, MsgPackSerializer, Plugin, PluginCommand};
 
 mod cool_custom_value;
 mod second_custom_value;
@@ -14,7 +12,7 @@ mod update_arg;
 use drop_check::{DropCheck, DropCheckValue};
 use generate::Generate;
 use generate2::Generate2;
-use nu_protocol::CustomValue;
+use nu_protocol::{CustomValue, LabeledError};
 use update::Update;
 use update_arg::UpdateArg;
 

crates/nu_plugin_custom_values/src/update.rs

@@ -2,8 +2,10 @@ use crate::{
     cool_custom_value::CoolCustomValue, second_custom_value::SecondCustomValue, CustomValuePlugin,
 };
 
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginExample, PluginSignature, ShellError, Span, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{
+    Category, LabeledError, PluginExample, PluginSignature, ShellError, Span, Value,
+};
 
 pub struct Update;
 

crates/nu_plugin_custom_values/src/update_arg.rs

@@ -1,7 +1,7 @@
 use crate::{update::Update, CustomValuePlugin};
 
-use nu_plugin::{EngineInterface, EvaluatedCall, LabeledError, SimplePluginCommand};
-use nu_protocol::{Category, PluginSignature, SyntaxShape, Value};
+use nu_plugin::{EngineInterface, EvaluatedCall, SimplePluginCommand};
+use nu_protocol::{Category, LabeledError, PluginSignature, SyntaxShape, Value};
 
 pub struct UpdateArg;