feat!: The HasTappableComponents mixin is no longer needed

[spydon]

Description

This PR is the second in a series of refactors that aim to simplify event handling in Flame. The approach is as follows:

• Added the MultiTapDispatcher component, which contains the logic that used to be within the HasTappableComponents mixin. This component is internal; it mounts to a FlameGame directly, and ensures that it is a singleton.
• Whenever any TapCallbacks component is added to a game, it automatically adds the MultiTapDispatcher component (unless there is already one), which in turn registers a tap gesture detector with GestureDetectorBuilder and rebuilds the game widget.

The end result is that now in order to make a component tappable you only need to add the TapCallbacks mixin to that component, everything else will be handled by the framework.

Consequently, the HasTappableComponents mixin is now empty and marked as deprecated.

Checklist

• I have followed the Contributor Guide when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.

Migration instructions

The HasTappableComponents mixin is now empty & deprecated. If your game used this mixin overriding its methods onTapDown, onTapUp, etc -- then they will no longer work. If you want to receive tap events at the top level of the game, then simply add a TapCallbacks component to the top level of the game.

Related Issues

WIP for #1733

[erickzanardo]

Great job 🔥! Overall LGTM, just left a couple of simple comments!

[erickzanardo]

LGTM awesome job!!!