Update the input mapping system to not dispatch both a matched KeyDown and KeyDownNoRepeat

For example, if we update `input_mapping.rs` like so:

```diff
- entry!(KeyDown(KeyA); action_dispatch=ToolMessage::ActivateToolPath),
+ entry!(KeyDownNoRepeat(KeyA); action_dispatch=ToolMessage::ActivateToolPath),
```

Then CtrlA will fire both the selection of all layers...

```
entry!(KeyDown(KeyA); modifiers=[Accel], action_dispatch=DocumentMessage::SelectAllLayers),
```

...as well as the change to the Path tool, since one gets matched on `KeyDown` and another on `KeyDownNoRepeat`. If both were `KeyDown` or `KeyDownNoRepeat`, only one would match. But currently, both are matching, and we only want one to match.

After implementing this fix, the following mappings should be changed from `KeyDown` to `KeyDownNoRepeat`:

Mappings to change

```
// TransformLayerMessage
entry!(KeyDown(KeyX); action_dispatch=TransformLayerMessage::ConstrainX),
entry!(KeyDown(KeyY); action_dispatch=TransformLayerMessage::ConstrainY),

// PathToolMessage
entry!(KeyDown(KeyG); action_dispatch=PathToolMessage::GRS { key: KeyG }),
entry!(KeyDown(KeyR); action_dispatch=PathToolMessage::GRS { key: KeyR }),
entry!(KeyDown(KeyS); action_dispatch=PathToolMessage::GRS { key: KeyS }),

// PenToolMessage
entry!(KeyDown(KeyG); action_dispatch=PenToolMessage::GRS { grab: KeyG, rotate: KeyR, scale: KeyS }),
entry!(KeyDown(KeyR); action_dispatch=PenToolMessage::GRS { grab: KeyG, rotate: KeyR, scale: KeyS }),
entry!(KeyDown(KeyS); action_dispatch=PenToolMessage::GRS { grab: KeyG, rotate: KeyR, scale: KeyS }),

// ToolMessage
entry!(KeyDown(KeyV); action_dispatch=ToolMessage::ActivateToolSelect),
entry!(KeyDown(KeyZ); action_dispatch=ToolMessage::ActivateToolNavigate),
entry!(KeyDown(KeyI); action_dispatch=ToolMessage::ActivateToolEyedropper),
entry!(KeyDown(KeyT); action_dispatch=ToolMessage::ActivateToolText),
entry!(KeyDown(KeyF); action_dispatch=ToolMessage::ActivateToolFill),
entry!(KeyDown(KeyH); action_dispatch=ToolMessage::ActivateToolGradient),
entry!(KeyDown(KeyA); action_dispatch=ToolMessage::ActivateToolPath),
entry!(KeyDown(KeyP); action_dispatch=ToolMessage::ActivateToolPen),
entry!(KeyDown(KeyN); action_dispatch=ToolMessage::ActivateToolFreehand),
entry!(KeyDown(KeyL); action_dispatch=ToolMessage::ActivateToolLine),
entry!(KeyDown(KeyM); action_dispatch=ToolMessage::ActivateToolRectangle),
entry!(KeyDown(KeyE); action_dispatch=ToolMessage::ActivateToolEllipse),
entry!(KeyDown(KeyY); action_dispatch=ToolMessage::ActivateToolPolygon),
entry!(KeyDown(KeyB); action_dispatch=ToolMessage::ActivateToolBrush),

// DocumentMessage
entry!(KeyDown(Space); modifiers=[Control], action_dispatch=DocumentMessage::GraphViewOverlayToggle),
entry!(KeyDown(KeyO); modifiers=[Alt], action_dispatch=DocumentMessage::ToggleOverlaysVisibility),
entry!(KeyDown(KeyS); modifiers=[Alt], action_dispatch=DocumentMessage::ToggleSnapping),
entry!(KeyDown(KeyL); modifiers=[Accel], action_dispatch=DocumentMessage::ToggleSelectedLocked),
entry!(KeyDown(KeyG); modifiers=[Alt], action_dispatch=DocumentMessage::ToggleGridVisibility),

// TransformLayerMessage
entry!(KeyDown(KeyG); action_dispatch=TransformLayerMessage::BeginGrab),
entry!(KeyDown(KeyR); action_dispatch=TransformLayerMessage::BeginRotate),
entry!(KeyDown(KeyS); action_dispatch=TransformLayerMessage::BeginScale),

// PortfolioMessage
entry!(KeyDown(KeyO); modifiers=[Accel], action_dispatch=PortfolioMessage::OpenDocument),
entry!(KeyDown(KeyI); modifiers=[Accel], action_dispatch=PortfolioMessage::Import),
entry!(KeyDown(KeyR); modifiers=[Alt], action_dispatch=PortfolioMessage::ToggleRulers),

// DialogMessage
entry!(KeyDown(KeyE); modifiers=[Accel], action_dispatch=DialogMessage::RequestExportDialog),
entry!(KeyDown(KeyN); modifiers=[Accel], action_dispatch=DialogMessage::RequestNewDocumentDialog),
entry!(KeyDown(Comma); modifiers=[Accel], action_dispatch=DialogMessage::RequestPreferencesDialog),
```