Allow plugins to report their own version and store it in the registry (#12883)

# Description

This allows plugins to report their version (and potentially other
metadata in the future). The version is shown in `plugin list` and in
`version`.

The metadata is stored in the registry file, and reflects whatever was
retrieved on `plugin add`, not necessarily the running binary. This can
help you to diagnose if there's some kind of mismatch with what you
expect. We could potentially use this functionality to show a warning or
error if a plugin being run does not have the same version as what was
in the cache file, suggesting `plugin add` be run again, but I haven't
done that at this point.

It is optional, and it requires the plugin author to make some code
changes if they want to provide it, since I can't automatically
determine the version of the calling crate or anything tricky like that
to do it.

Example:

```
> plugin list | select name version is_running pid
╭───┬────────────────┬─────────┬────────────┬─────╮
│ # │      name      │ version │ is_running │ pid │
├───┼────────────────┼─────────┼────────────┼─────┤
│ 0 │ example        │ 0.93.1  │ false      │     │
│ 1 │ gstat          │ 0.93.1  │ false      │     │
│ 2 │ inc            │ 0.93.1  │ false      │     │
│ 3 │ python_example │ 0.1.0   │ false      │     │
╰───┴────────────────┴─────────┴────────────┴─────╯
```

cc @maxim-uvarov (he asked for it)

# User-Facing Changes

- `plugin list` gets a `version` column
- `version` shows plugin versions when available
- plugin authors *should* add `fn metadata()` to their `impl Plugin`,
but don't have to

# Tests + Formatting

Tested the low level stuff and also the `plugin list` column.

# After Submitting
- [ ] update plugin guide docs
- [ ] update plugin protocol docs (`Metadata` call & response)
- [ ] update plugin template (`fn metadata()` should be easy)
- [ ] release notes

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

@@ -118,11 +118,12 @@ apparent the next time `nu` is next launched with that plugin registry file.
             },
         ));
         let interface = plugin.clone().get_plugin(Some((engine_state, stack)))?;
+        let metadata = interface.get_metadata()?;
         let commands = interface.get_signature()?;
 
         modify_plugin_file(engine_state, stack, call.head, custom_path, |contents| {
-            // Update the file with the received signatures
-            let item = PluginRegistryItem::new(plugin.identity(), commands);
+            // Update the file with the received metadata and signatures
+            let item = PluginRegistryItem::new(plugin.identity(), metadata, commands);
             contents.upsert_plugin(item);
             Ok(())
         })?;

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

@@ -16,6 +16,7 @@ impl Command for PluginList {
                 Type::Table(
                     [
                         ("name".into(), Type::String),
+                        ("version".into(), Type::String),
                         ("is_running".into(), Type::Bool),
                         ("pid".into(), Type::Int),
                         ("filename".into(), Type::String),
@@ -43,6 +44,7 @@ impl Command for PluginList {
                 description: "List installed plugins.",
                 result: Some(Value::test_list(vec![Value::test_record(record! {
                     "name" => Value::test_string("inc"),
+                    "version" => Value::test_string(env!("CARGO_PKG_VERSION")),
                     "is_running" => Value::test_bool(true),
                     "pid" => Value::test_int(106480),
                     "filename" => if cfg!(windows) {
@@ -98,8 +100,15 @@ impl Command for PluginList {
                 .map(|s| Value::string(s.to_string_lossy(), head))
                 .unwrap_or(Value::nothing(head));
 
+            let metadata = plugin.metadata();
+            let version = metadata
+                .and_then(|m| m.version)
+                .map(|s| Value::string(s, head))
+                .unwrap_or(Value::nothing(head));
+
             let record = record! {
                 "name" => Value::string(plugin.identity().name(), head),
+                "version" => version,
                 "is_running" => Value::bool(plugin.is_running(), head),
                 "pid" => pid,
                 "filename" => Value::string(plugin.identity().filename().to_string_lossy(), head),