keymap_ui: Add context menu for table rows (#33747)

Closes #ISSUE

Adds a right click context menu to table rows, refactoring the table API
to support more general row rendering in the process, and creating
actions for the couple of operations available in the context menu.

Additionally includes an only partially related change to the context
menu API, which makes it easier to have actions that are disabled based
on a boolean value.

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/zed/src/zed.rs

@@ -4311,6 +4311,7 @@ mod tests {
                 "icon_theme_selector",
                 "jj",
                 "journal",
+                "keymap_editor",
                 "language_selector",
                 "lsp_tool",
                 "markdown",