Input HUD: Use consistent input button icons

[wjt]

Previously we had a mixture of outline and filled icons; and of colour
and monochrome icons for Xbox and PlayStation.

Refactor the way that these icons are assigned so that they are stored
in the same JoypadButtonTextures resource as directional inputs. This
means that the textures for a device type can be configured all in one
place.

Consistently use outline icons, which are more legible and obscure less of the world.

Consistently use monochrome icons for Xbox. It is true
that official Xbox controllers do have colours on the A/B/X/Y buttons
but looking at some photos in an image search, the colours are either
used for the text (not the surrounding button), or are printed as a
little directional key in between the four buttons. I own two Xbox-style
controllers made by 8BitDo; they use the XBox RB/RT labels for shoulder
buttons rather than R1/R2 so the use of xbox textures for generic
controllers seems appropriate, but they do not use colours.

Similarly, use monochrome icons for PlayStation. Some PlayStation
controllers have coloured buttons, but many more do not, and I don't
think the colours are the strongest association.

Some of the Switch button textures were inconsistent with the input map;
fix these in the process. Unfortunately I was unable to pair my Switch 2
JoyCons with my laptop so I can't actually test these. (If we wanted to
support Switch controllers "properly", IMO we should swap the mappings
so that the Switch "A" button is interact, but that's one for another
lifetime.)

For champ_stealth, rather than adding these champ_specific actions to
the global input map, make interact_input.gd skip the per-device mapping
if it is not provided, which improves on the previous behaviour of
showing blank icons when using a controller.

For Sueños Nocturnos, which has a custom "Saltar cinemática." hint, use
the "interact" button (matching the previous hardcoded button textures),
and adjust the action it looks for to match so that joypad buttons
actually work.

[github-actions]

Play this branch at https://play.threadbare.game/branches/endlessm/wjt/input-hud-use-consistent-input-button-icons/.

(This launches the game from the start, not directly at the change(s) in this pull request.)

[wjt]

Before	After (filled)	After (outline)

[manuq]

Yes great, the button icons should be consistent!

By looking at these screenshots and playing the branch, I find the outline versions better to the eye for readability and less intrusive, as they let seeing more of the world behind them.

In particular the filled icon for Shift is a bit unreadable:

Than:

But yes in general I agree with making all of the buttons consistent. Initially I thought that color icons were used because there weren't monochrome counterparts to use. But they are there!

[manuq]

@jofilizola you may have feedback for this as well.

[wjt]

OK, I defer to more visually-skilled people on whether the filled or outline versions appear better - your pair of screenshots has convinced me. I'll revise this to use outline versions. We can try #2167 too - it looks good!

[wjt]

I'll land this with consistent monochrome, outline icons; we can always iterate.