A set of outline panel fixes (#12965)

Follow-up of https://github.com/zed-industries/zed/pull/12637

* Wrong font size for the outline items (fixes
https://github.com/zed-industries/zed/pull/12637#issuecomment-2164084021)
* Duplicate context menu item (fixes
https://github.com/zed-industries/zed/issues/12957)
* Missing `space` keybinding for item opening (fixes
https://github.com/zed-industries/zed/issues/12956)
* Adds 60px more to the default width (fixes
https://github.com/zed-industries/zed/issues/12955)
* Incorrect scroll for singleton buffers (fixes
https://github.com/zed-industries/zed/issues/12953)

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -566,11 +566,12 @@
   {
     "context": "OutlinePanel",
     "bindings": {
-      "left": "project_panel::CollapseSelectedEntry",
-      "right": "project_panel::ExpandSelectedEntry",
-      "ctrl-alt-c": "project_panel::CopyPath",
-      "alt-ctrl-shift-c": "project_panel::CopyRelativePath",
-      "alt-ctrl-r": "project_panel::RevealInFinder",
+      "left": "outline_panel::CollapseSelectedEntry",
+      "right": "outline_panel::ExpandSelectedEntry",
+      "ctrl-alt-c": "outline_panel::CopyPath",
+      "alt-ctrl-shift-c": "outline_panel::CopyRelativePath",
+      "alt-ctrl-r": "outline_panel::RevealInFinder",
+      "space": "outline_panel::Open",
       "shift-down": "menu::SelectNext",
       "shift-up": "menu::SelectPrev"
     }

assets/keymaps/default-macos.json

@@ -593,6 +593,7 @@
       "cmd-alt-c": "outline_panel::CopyPath",
       "alt-cmd-shift-c": "outline_panel::CopyRelativePath",
       "alt-cmd-r": "outline_panel::RevealInFinder",
+      "space": "outline_panel::Open",
       "shift-down": "menu::SelectNext",
       "shift-up": "menu::SelectPrev"
     }

assets/settings/default.json

@@ -131,14 +131,7 @@
   // The default number of lines to expand excerpts in the multibuffer by.
   "expand_excerpt_lines": 3,
   // Globs to match against file paths to determine if a file is private.
-  "private_files": [
-    "**/.env*",
-    "**/*.pem",
-    "**/*.key",
-    "**/*.cert",
-    "**/*.crt",
-    "**/secrets.yml"
-  ],
+  "private_files": ["**/.env*", "**/*.pem", "**/*.key", "**/*.cert", "**/*.crt", "**/secrets.yml"],
   // Whether to use additional LSP queries to format (and amend) the code after
   // every "trigger" symbol input, defined by LSP server capabilities.
   "use_on_type_format": true,
@@ -306,7 +299,7 @@
     // Whether to show the outline panel button in the status bar
     "button": true,
     // Default width of the outline panel.
-    "default_width": 240,
+    "default_width": 300,
     // Where to dock the outline panel. Can be 'left' or 'right'.
     "dock": "left",
     // Whether to show file icons in the outline panel.