Go to Implementation is missing in main Navigate menu

### Description

_Go to Implementation_ (Ctrl+Alt+B) exists in the context menu in the editor (under _Navigate_), but is missing in the main _Navigate_ menu. The main menu has _Go to Source/Declaration/Super Implementation_ and _Inspect_, while the context menu additionally has _Go to Implementation_. It would be useful to make the main menu consistent with the context menu here.

### Use case/motivation

Since the main menu has _Go to Super Implementation_, it makes sense for it to also have _Go to Implementation_. The main menu is more obvious/accessible than the context menu, and it is also helpful to look up keyboard shortcuts more quickly.

### Related issues

_No response_

### Are you willing to submit a pull request?

No

Start by comparing the editor context menu's Navigate actions with the main Navigate menu, focusing on the existing Go to Implementation action and its Ctrl+Alt+B shortcut. Locate the menu/action registration used by these entries and expose the same action in the main menu; done means both menus provide Go to Implementation and the shortcut remains discoverable.

Written by the indexing model from the issue text.