Fix incorrect ActionData::axis_pair value when handling multiple DualAxisData

[Shute052]

Objective

The previous PR (#450) removed the accumulation for ActionData::axis_pair in InputMap::which_pressed(), resulting in a problem where multiple DualAxisData updates would only preserve the last one due to the loss of previously recorded DualAxisData.

A Simple Reproduction Case

InputMap::new([
        (Action, VirtualDPad::arrow_keys()),
        (Action, VirtualDPad::wasd()),
]);

While it functions correctly when pressing WASD, if only the arrow keys were pressed, ActionState::axis_pair() will return None.

Solution

Re-implement the accumulation of ActionData::axis_pair in InputMap::which_pressed().

Changelog

• Re-add the accumulation of ActionData::axis_pair
• Simplify the ButtonState::JustPressed check by moving it into the input_pressed checking block and remove the pressed flag

[Hellzbellz123]

this fixes the issue i commented about on discord, glad someone figured out what was actually wrong

[alice-i-cecile]

Thank you!