More efficient FluidButton

[KyleRAnderson]

It's possible that part of the reason that the robot is overruning it's loop time was because the FluidButton always looks up the Xbox button port each time it runs the get() method.

Fixed by using the FluidConstant listener instead.

Summary of Changes

• FluidButton doesn't poll the joystick port from the fluid constant each time get() is called.
• Instead, listeners are used to update the value in memory when it changes.

Testing Performed

Environment: Automated testing.

Awaiting more testing.

[KyleRAnderson]

It's still a draft @eandr127 😂.

[KyleRAnderson]

@eandr127 tested this on practice bot and it worked. Changed the fluid constant binding in the outline viewer and confirmed that it updated.