Add cursor_shape setting for the default editor (#17572)

Closes https://github.com/zed-industries/zed/issues/16451,
https://github.com/zed-industries/zed/issues/14447,
https://github.com/zed-industries/zed/issues/7203

Addresses but does not closes
https://github.com/zed-industries/zed/issues/5179

Expose cursor shape selection to users. Possibly controversial, since
block cursor seems preserved for vim and terminal. But the heart wants
what it wants?

Release Notes:

- Added a setting for `cursor_shape`. Can be `bar`, `block`,
`underline`, or `hollow`. Default is `bar`.

crates/language/src/buffer.rs

@@ -26,6 +26,8 @@ use gpui::{
 };
 use lsp::LanguageServerId;
 use parking_lot::Mutex;
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
 use serde_json::Value;
 use settings::WorktreeId;
 use similar::{ChangeTag, TextDiff};
@@ -161,7 +163,8 @@ pub enum IndentKind {
 }
 
 /// The shape of a selection cursor.
-#[derive(Copy, Clone, PartialEq, Eq, Debug, Default)]
+#[derive(Copy, Clone, Debug, Default, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
+#[serde(rename_all = "snake_case")]
 pub enum CursorShape {
     /// A vertical bar
     #[default]