Remove bottom dock layout button (#28876)

Release Notes:

- Preview: Removed the layout button from the title bar. The
`bottom_dock_layout` setting still functions.
- Added a setting, `bottom_dock_layout`, for controlling the
relationship between the bottom dock and the left and right docks.

docs/src/configuring-zed.md

@@ -75,6 +75,46 @@ Non-negative `float` values
 
 `float` values
 
+## Bottom Dock Layout
+
+- Description: Control the layout of the bottom dock, relative to the left and right docks
+- Setting: `bottom_dock_layout`
+- Default: `"contained"`
+
+**Options**
+
+1. Contain the bottom dock, giving the full height of the window to the left and right docks
+
+```json
+{
+  "bottom_dock_layout": "contained"
+}
+```
+
+2. Give the bottom dock the full width of the window, truncating the left and right docks
+
+```json
+{
+  "bottom_dock_layout": "full"
+}
+```
+
+3. Left align the bottom dock, truncating the left dock and giving the right dock the full height of the window
+
+```json
+{
+  "bottom_dock_layout": "left_aligned"
+}
+```
+
+3. Right align the bottom dock, giving the left dock the full height of the window and truncating the right dock.
+
+```json
+{
+  "bottom_dock_layout": "right_aligned"
+}
+```
+
 ## Auto Install extensions
 
 - Description: Define extensions to be autoinstalled or never be installed.