Allow resetting celestial vault elements by leaving its arguments empty

[Zughy]

• How does the PR work? set_sky() etc, when left blank, reset that part of the celestial vault to its default
• Does it resolve any reported issue? Fixes Leave set_sky() etc. with no arguments to reset a player's celestial vault #11916
• Does this relate to a goal in the roadmap? 2.4, API convenience
• How about the dummy image error it generates? Not this PR's fault, see set_sun/set_moon: setting textures to something and then to their default name again creates dummy broken images #11930

To do

This PR is Ready for Review.

How to test

minetest.register_on_joinplayer(function(player)
    
    local sky = {
        sky_color = {
            day_sky = "#ffffff"    
        }
    }
    
    local sun = {
        texture = "cdb_queued.png",
        size = 2
    }
    
    local moon = {
        texture = "bubble.png",
        size = 2
    }
    
    local stars = {
        count = 3000,
        scale = 0.5
    }
    
    local clouds = {
        thickness = 50,
        height = 30,
        speed = { x = 0.1, z = 5 }
    }
    
    player:set_sky(sky)
    player:set_sun(sun)
    player:set_moon(moon)
    player:set_stars(stars)
    player:set_clouds(clouds)
    
    minetest.after(3, function()
        player:set_sky()
        player:set_sun()
        player:set_moon()
        player:set_stars()
        player:set_clouds()
    end)
end)

[Zughy]

Done. Reviewing commit by commit should make your life easier. Also, I got rid of cloudparams.h because it was only a file with a struct that could have been declared in skyparams.h

[Zughy]

In order to work 100%, this PR needs what has been highlighted in #11930 first. The PR does the job is expected to, just, there is another problem in the way that causes the dummy image error in here

[Zughy]

@SmallJoker done

[SmallJoker]

Looks good.

[sfan5]

In order to work 100%, this PR needs what has been highlighted in #11930 first.

^ Is this the case now or ...?

[Zughy]

@sfan5 poor wording, my bad. I meant that the snippet throws in chat the missing image error I pointed out in the other issue (when it resets moon and sun), but it's not something related to this PR, it's not something I've altered

[Zughy]

@sfan5 done

[sfan5]

You accidentally committed client/mod_storage.sqlite, please remove.

[Zughy]

Wait what how-
@sfan5 done

[Zughy]

@sfan5 the PR still stays "action / change needed", I guess you misclicked?

[sfan5]

I'm suggesting you put the fix from #11930 into this PR.

[Zughy]

That's not related to this PR nor I know where to put my hands (I tried last week). It's a free PR that does what's intended already :\

[sfan5]

I literally provided a diff of the fix, but okay, I did it myself.

[Zughy]

...I didn't see the notification about the other issue, I'm sorry

[Zughy]

Wait, so this won't cause any problems with texture packs shipping sun.png and moon.png by default such as RPG16? https://gitlab.com/Df458/rpg16/-/tree/master/misc

[sfan5]

You're right. The reason is that at startup the sky picks sun.png if it exists and else uses the mesh sun. If you ever change the texture it is impossible to return to this state.
Whatever, I'll fix it in a separate PR.