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/workspace/src/pane_group.rs

@@ -13,6 +13,7 @@ use gpui::{
 };
 use parking_lot::Mutex;
 use project::Project;
+use schemars::JsonSchema;
 use serde::Deserialize;
 use settings::Settings;
 use std::sync::Arc;
@@ -717,7 +718,7 @@ impl PaneAxis {
     }
 }
 
-#[derive(Clone, Copy, Debug, Deserialize, PartialEq)]
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, JsonSchema)]
 pub enum SplitDirection {
     Up,
     Down,
@@ -800,7 +801,7 @@ impl SplitDirection {
     }
 }
 
-#[derive(Clone, Copy, Debug, Deserialize, PartialEq)]
+#[derive(Clone, Copy, Debug, Deserialize, JsonSchema, PartialEq)]
 pub enum ResizeIntent {
     Lengthen,
     Shorten,