Add ability to hide status bar (#39430)

This pull request adds the ability to configure the setting to hide or
show the status bar, as described in discussion:
https://github.com/zed-industries/zed/discussions/38591

The original [PR
#38974](https://github.com/zed-industries/zed/pull/38974#issuecomment-3362020879)
was merged but reverted due to hidden conflicts. As per @ConradIrwin 's
[request](https://github.com/zed-industries/zed/pull/38974#issuecomment-3362020879),
I am recreating the PR on top of updated main branch.

Release Notes:

- Added an experimental setting `"status_bar": { "experimental.show":
false}` to hide the status bars.

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

assets/settings/default.json

@@ -1329,6 +1329,8 @@
   },
   // Status bar-related settings.
   "status_bar": {
+    // Whether to show the status bar.
+    "experimental.show": true,
     // Whether to show the active language button in the status bar.
     "active_language_button": true,
     // Whether to show the cursor position button in the status bar.