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-plugin-test-support/src/fake_persistent_plugin.rs

@@ -6,7 +6,7 @@ use std::{
 use nu_plugin_engine::{GetPlugin, PluginInterface};
 use nu_protocol::{
     engine::{EngineState, Stack},
-    PluginGcConfig, PluginIdentity, RegisteredPlugin, ShellError,
+    PluginGcConfig, PluginIdentity, PluginMetadata, RegisteredPlugin, ShellError,
 };
 
 pub struct FakePersistentPlugin {
@@ -42,6 +42,12 @@ impl RegisteredPlugin for FakePersistentPlugin {
         None
     }
 
+    fn metadata(&self) -> Option<PluginMetadata> {
+        None
+    }
+
+    fn set_metadata(&self, _metadata: Option<PluginMetadata>) {}
+
     fn set_gc_config(&self, _gc_config: &PluginGcConfig) {
         // We don't have a GC
     }

crates/nu-plugin-test-support/src/lib.rs

@@ -66,6 +66,10 @@
 //! }
 //!
 //! impl Plugin for LowercasePlugin {
+//!     fn version(&self) -> String {
+//!         env!("CARGO_PKG_VERSION").into()
+//!     }
+//!
 //!     fn commands(&self) -> Vec<Box<dyn PluginCommand<Plugin=Self>>> {
 //!         vec![Box::new(Lowercase)]
 //!     }

crates/nu-plugin-test-support/tests/custom_value/mod.rs

@@ -53,6 +53,10 @@ struct IntoU32;
 struct IntoIntFromU32;
 
 impl Plugin for CustomU32Plugin {
+    fn version(&self) -> String {
+        "0.0.0".into()
+    }
+
     fn commands(&self) -> Vec<Box<dyn nu_plugin::PluginCommand<Plugin = Self>>> {
         vec![Box::new(IntoU32), Box::new(IntoIntFromU32)]
     }

crates/nu-plugin-test-support/tests/hello/mod.rs

@@ -8,6 +8,10 @@ struct HelloPlugin;
 struct Hello;
 
 impl Plugin for HelloPlugin {
+    fn version(&self) -> String {
+        "0.0.0".into()
+    }
+
     fn commands(&self) -> Vec<Box<dyn PluginCommand<Plugin = Self>>> {
         vec![Box::new(Hello)]
     }

crates/nu-plugin-test-support/tests/lowercase/mod.rs

@@ -59,6 +59,10 @@ impl PluginCommand for Lowercase {
 }
 
 impl Plugin for LowercasePlugin {
+    fn version(&self) -> String {
+        "0.0.0".into()
+    }
+
     fn commands(&self) -> Vec<Box<dyn PluginCommand<Plugin = Self>>> {
         vec![Box::new(Lowercase)]
     }