Adjust input HUD during dialogue

[wjt]

Now that we always show input hints for player movement or Sokoban controls, it is confusing that they are displayed during dialogue:

We should swap these for dialogue-specific hints during dialogue.

The actions depend on what stage the dialogue is at:

• If the dialogue is being typed, Skip can be used
• If the dialogue is waiting for the player to choose from a number of responses, the up/down arrows and the next/accept/interact button can be used to choose
• Otherwise, dialogue_next can be used to advance to the next line of dialogue (possibly ending the dialogue, c.f. "Next →" button in one-line dialogue is confusing #1846)

XP Summary (total 450)

Subdomain	Skill	XP
Game Design: Game Feel & UX	Problem Solving	75
Game Design: Game Feel & UX	Creativity & Design Thinking	75
Game Design: Game Feel & UX	Technical Literacy	75
Engineering: Gameplay & Systems Programming	Problem Solving	75
Engineering: Gameplay & Systems Programming	Creativity & Design Thinking	75
Engineering: Gameplay & Systems Programming	Technical Literacy	75

[wjt]

From an implementation point of view, just detecting whether dialogue is playing can be done with the DialogueManager.dialogue_started and DialogueManager.dialogue_ended signals.

More details are a bit harder to come by - it will mean using the API of the balloon itself.