Improve Linux terminal keymap and context menu (#16845)

Follow-up https://github.com/zed-industries/zed/pull/16085 that fixes
the search deploy to be actually a part of the terminal-related
bindings.

Part of https://github.com/zed-industries/zed/issues/16839

Also 

* fixes few other bindings to use `shift` and avoid conflicts with the
existing key bindings.
* adds terminal inline assist to the context menu and makes both the
menu and the button to dynamically adjust to `assist.enabled` settings
change

It is still unclear to me, why certain labels for certain bindings are
wrong (it's still showing `ctrl-w` for closing the terminal tab, and
`shift-insert` instead of `ctrl-shift-v` for Paste, while Insert is near
and has a `ctrl-shift-c` binding shown) but at least the keys work now.

Release notes: 
- Improved Linux terminal keymap and context menu

crates/zed_actions/src/lib.rs

@@ -40,3 +40,10 @@ actions!(
         ResetUiFontSize
     ]
 );
+
+#[derive(Clone, Default, Deserialize, PartialEq)]
+pub struct InlineAssist {
+    pub prompt: Option<String>,
+}
+
+impl_actions!(assistant, [InlineAssist]);