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>

docs/src/configuring-zed.md

@@ -1502,6 +1502,14 @@ Positive `integer` value between 1 and 32. Values outside of this range will be
 },
 ```
 
+There is an experimental setting that completely hides the status bar. This causes major usability problems (you will be unable to use many of Zed's features), but is provided for those who value screen real-estate above all else.
+
+```json
+"status_bar": {
+  "experimental.show": false
+}
+```
+
 ## LSP
 
 - Description: Configuration for language servers.