vim: Support za (#18421)

Closes #6822
Updates #5142 

Release Notes:

- Added new fold actions to toggle folds (`cmd-k cmd-l`), fold every
fold (`cmd-k cmd-0`) unfold every fold (`cmd-k cmd-j`) to fold
recursively (`cmd-k cmd-[`) and unfold recursively (`cmd-k cmd-]`).
- vim: Added `za` to toggle fold under cursor.
- vim: Added `zO`/`zC`/`zA` to open, close and toggle folds recursively
(and fixed `zc` to not recurse into selections).
- vim: Added `zR`/`zM` to open/close all folds in the buffer.

assets/keymaps/default-linux.json

@@ -310,6 +310,11 @@
       "ctrl-shift-\\": "editor::MoveToEnclosingBracket",
       "ctrl-shift-[": "editor::Fold",
       "ctrl-shift-]": "editor::UnfoldLines",
+      "ctrl-k ctrl-l": "editor::ToggleFold",
+      "ctrl-k ctrl-[": "editor::FoldRecursive",
+      "ctrl-k ctrl-]": "editor::UnfoldRecursive",
+      "ctrl-k ctrl-0": "editor::FoldAll",
+      "ctrl-k ctrl-j": "editor::UnfoldAll",
       "ctrl-space": "editor::ShowCompletions",
       "ctrl-.": "editor::ToggleCodeActions",
       "alt-ctrl-r": "editor::RevealInFileManager",

assets/keymaps/default-macos.json

@@ -347,6 +347,11 @@
       "cmd-shift-\\": "editor::MoveToEnclosingBracket",
       "alt-cmd-[": "editor::Fold",
       "alt-cmd-]": "editor::UnfoldLines",
+      "cmd-k cmd-l": "editor::ToggleFold",
+      "cmd-k cmd-[": "editor::FoldRecursive",
+      "cmd-k cmd-]": "editor::UnfoldRecursive",
+      "cmd-k cmd-0": "editor::FoldAll",
+      "cmd-k cmd-j": "editor::UnfoldAll",
       "ctrl-space": "editor::ShowCompletions",
       "cmd-.": "editor::ToggleCodeActions",
       "alt-cmd-r": "editor::RevealInFileManager",

assets/keymaps/vim.json

@@ -132,9 +132,15 @@
       "z z": "editor::ScrollCursorCenter",
       "z .": ["workspace::SendKeystrokes", "z z ^"],
       "z b": "editor::ScrollCursorBottom",
+      "z a": "editor::ToggleFold",
+      "z A": "editor::ToggleFoldRecursive",
       "z c": "editor::Fold",
+      "z C": "editor::FoldRecursive",
       "z o": "editor::UnfoldLines",
+      "z O": "editor::UnfoldRecursive",
       "z f": "editor::FoldSelectedRanges",
+      "z M": "editor::FoldAll",
+      "z R": "editor::UnfoldAll",
       "shift-z shift-q": ["pane::CloseActiveItem", { "saveIntent": "skip" }],
       "shift-z shift-z": ["pane::CloseActiveItem", { "saveIntent": "saveAll" }],
       // Count support