Improve keymap json schema (#23044)

Also:

* Adds `impl_internal_actions!` for deriving the `Action` trait without
registering.

* Removes some deserializers that immediately fail in favor of
`#[serde(skip)]` on fields where they were used. This also omits them
from the schema.

Release Notes:

- Keymap settings file now has more JSON schema information to inform
`json-language-server` completions and info, particularly for actions
that take input.

crates/tab_switcher/Cargo.toml

@@ -19,6 +19,7 @@ gpui.workspace = true
 menu.workspace = true
 picker.workspace = true
 project.workspace = true
+schemars.workspace = true
 serde.workspace = true
 settings.workspace = true
 ui.workspace = true

crates/tab_switcher/src/tab_switcher.rs

@@ -10,6 +10,7 @@ use gpui::{
 };
 use picker::{Picker, PickerDelegate};
 use project::Project;
+use schemars::JsonSchema;
 use serde::Deserialize;
 use settings::Settings;
 use std::sync::Arc;
@@ -23,7 +24,7 @@ use workspace::{
 
 const PANEL_WIDTH_REMS: f32 = 28.;
 
-#[derive(PartialEq, Clone, Deserialize, Default)]
+#[derive(PartialEq, Clone, Deserialize, JsonSchema, Default)]
 pub struct Toggle {
     #[serde(default)]
     pub select_last: bool,