[GLIMMER2] Click action links instead of touching action manager internals

[zackthehuman]

This should fix the following tests listed in #13644:

• Events are triggered on the controller if a matching action name is implemented
• Events are triggered on the current state when defined in actions object
• Events defined in actions object are triggered on the current state when routes are nested
• Actions are not triggered on the controller if a matching action name is implemented as a method
• actions can be triggered with multiple arguments

The ActionManager internals differ between HTMLBars and Glimmer2, and the tests were written in a way that relied on the implementation details. This change simplifies things by doing what a user would do: click on the thing.

[chadhietala]

LGTM and actually makes the tests less about the "how".

[rwjblue]

Thanks @zackthehuman!