terminal: Make CursorShape configurable (#18530)

This builds on top of @Yevgen's #15840 and combines it with the settings
names introduced in #17572.

Closes #4731.

Release Notes:

- Added a setting for the terminal's default cursor shape. The setting
is `{"terminal": {"cursor_shape": "block"}}``. Possible values: `block`,
`bar`, `hollow`, `underline`.

Demo:


https://github.com/user-attachments/assets/96ed28c2-c222-436b-80cb-7cd63eeb47dd

crates/terminal/src/terminal_settings.rs

@@ -1,3 +1,6 @@
+use alacritty_terminal::vte::ansi::{
+    CursorShape as AlacCursorShape, CursorStyle as AlacCursorStyle,
+};
 use collections::HashMap;
 use gpui::{
     px, AbsoluteLength, AppContext, FontFallbacks, FontFeatures, FontWeight, Pixels, SharedString,
@@ -32,6 +35,7 @@ pub struct TerminalSettings {
     pub font_weight: Option<FontWeight>,
     pub line_height: TerminalLineHeight,
     pub env: HashMap<String, String>,
+    pub cursor_shape: Option<CursorShape>,
     pub blinking: TerminalBlink,
     pub alternate_scroll: AlternateScroll,
     pub option_as_meta: bool,
@@ -129,6 +133,11 @@ pub struct TerminalSettingsContent {
     ///
     /// Default: {}
     pub env: Option<HashMap<String, String>>,
+    /// Default cursor shape for the terminal.
+    /// Can be "bar", "block", "underscore", or "hollow".
+    ///
+    /// Default: None
+    pub cursor_shape: Option<CursorShape>,
     /// Sets the cursor blinking behavior in the terminal.
     ///
     /// Default: terminal_controlled
@@ -282,3 +291,37 @@ pub struct ToolbarContent {
     /// Default: true
     pub title: Option<bool>,
 }
+
+#[derive(Clone, Copy, Debug, Default, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
+#[serde(rename_all = "snake_case")]
+pub enum CursorShape {
+    /// Cursor is a block like `█`.
+    #[default]
+    Block,
+    /// Cursor is an underscore like `_`.
+    Underline,
+    /// Cursor is a vertical bar like `⎸`.
+    Bar,
+    /// Cursor is a hollow box like `▯`.
+    Hollow,
+}
+
+impl From<CursorShape> for AlacCursorShape {
+    fn from(value: CursorShape) -> Self {
+        match value {
+            CursorShape::Block => AlacCursorShape::Block,
+            CursorShape::Underline => AlacCursorShape::Underline,
+            CursorShape::Bar => AlacCursorShape::Beam,
+            CursorShape::Hollow => AlacCursorShape::HollowBlock,
+        }
+    }
+}
+
+impl From<CursorShape> for AlacCursorStyle {
+    fn from(value: CursorShape) -> Self {
+        AlacCursorStyle {
+            shape: value.into(),
+            blinking: false,
+        }
+    }
+}