Upstream additional GamePad code

https://bugs.webkit.org/show_bug.cgi?id=326113
rdar://problem/189026641

Reviewed by Tim Nguyen and Brady Eidson.

Move the remaining GameController code into open source. Also add the
Singleton suffix that the soft-linked constant getters now require.

* Source/WebCore/platform/gamepad/cocoa/GameControllerGamepadProvider.mm:
(WebCore::shouldExcludeGameController):
* Source/WebCore/platform/gamepad/cocoa/GameControllerSoftLink.h:
* Source/WebCore/platform/gamepad/cocoa/GameControllerSoftLink.mm:

Canonical link: https://commits.webkit.org/322773@main