Added Pressed event handler for when item is pressed.
Added Handlers for MouseEntered and Exited for highlighting of the item.
Added GuiInput override to handle Pressed events for Item.
Added StyleBoxFlat to Label, to show highlighting feedback of the item.
Removed Spacer, as it isn't needed.
Updated Label to take full rect of space available for the Label,
adjusted Vertical Alignment to be center.

Created new Custom Run Button UI, to handle Selecting a Startup Project
to run, while still offering a Menu to allow launching of multiple
projects.

Added new controls for Building, Running, Debugging, and Stopping the
Startup project.
Implemented logic to handle when there is a Change in the Startup
Project, and save it to the IdeSolutionState for the last Startup
Project setup.

Added signal for when the Run Button is pressed, to sync startup project
status.

Renamed signal StartupProjectChanged to ProjectChanged.
Added Signal ItemAdded to allow Project signals to be connected up the
chain.
Added Signal RunRequested to sync UI for Startup Project being launched
from menu.
Removed empty functions as going a different route for design.

Moved HBoxContainer into StartupProject control, to group together the
ProjectList Options, with the Run and Debug button controls for startup
project.

Removed no longer used RunMenuButton and RunMenuPopup has that is now
handled by the StartupProject control.
Changed code to use new StartupProject control.

Renamed control to better show what the control actually does.
Updated StartupProjec tto use new class name.

Added Keybinds to Run, Debug and Stop current Startup Project.

Added logic to handle new Run, Debug and Stop Startup Project.

Swapped Debug and Run shortcuts around, as most times during
development, you want to debug your project with an attached debugger
for exceptions.

Re-arranged to Run, Debug, and then Stop, added exactMatch to be true,
so that Keybinds with Modifiers don't trigger keybinds without
modifiers.