[data] Refactor resources folder

[AndrewShkrob]

New folder structure
From

• resources-mdpi-clear
• resources-mdpi-dark
• resources-xhdpi-clear
• resources-xhdpi-dark

To

symbols
├── 6plus
│   ├── clear
│   │   ├── symbols.png
│   │   └── symbols.sdf
│   ├── dark
│   │   ├── symbols.png
│   │   └── symbols.sdf
│   └── design
│       ├── symbols.png
│       └── symbols.sdf
├── hdpi
│   ├── clear
│   │   ├── symbols.png
│   │   └── symbols.sdf
│   ├── dark
│   │   ├── symbols.png
│   │   └── symbols.sdf
│   └── design
│       ├── symbols.png
│       ├── symbols.sdf

Moved area-hatching.png and traffic-arrow.png from {dpi}/{clear|dark} to symbols/default folder as all these files are the same and not regenerated.

Unfortunately, Xcode doesn't allow a resources folder in the root directory. I had to rename the folder from resources to symbols.
More info: https://stackoverflow.com/questions/33993741/codesign-failed-with-exit-code-1-failing-to-build-copy-resources/40167588#40167588

I cannot place resources-svg in symbols/svg due to another Xcode problem. It doesn't allow to have a reference folder and exclude one of the subfolders from the project.

[biodranik]

@AndrewShkrob did you see this one? WDYT? #7264

[AndrewShkrob]

@AndrewShkrob did you see this one? WDYT? #7264

light/dark is much better than clear/dark
We can postpone this PR until the #7264 is merged. I'll rebase it later.

[pastk]

Actually its different:
128x32 for mdpi
512x128 for xxxhdpi

[pastk]

Stuff in resources-svg is very different from "symbols.png".

Icons from resources-svg are used in apps' UI and AFAIK not directly, e.g. for android they have to be converted into vector drawable.

"symbols.png" are map icons (and other symbols) consumed by core and automatically generated via generate_symbols.sh.

So I think it makes sense to keep their names different to avoid confusion.
Maybe just leave "resources-svg" as is or rename to e.g. "UI-icons-svg"...

[pastk]

Moved area-hatching.png and traffic-arrow.png from {dpi}/{clear|dark} to symbols/default folder as all these files are the same and not regenerated.

So traffic arrows are different (compare mdpi to xxxhdpi).

area-hatching.png is the same for all dpis indeed.
But its very likely we'll expand handling of it to support other more complex textures like forest, shrub, hospital, etc. and they're likely to be dpi-dependent.. @vng WDYT?

[pastk]

Thanks for this PR, its a great companion to #7264!

Please check #7264 (comment)
i.e. there are dpi-specific folders in data/styles/clear/style-clear/ which would be great to move too!

[pastk]

Please check #7264 (comment) i.e. there are dpi-specific folders in data/styles/clear/style-clear/ which would be great to move too!

Though I'm not sure it'll be a good idea to put them into symbols/hdpi/... you've created.
Probably makes sense to keep "resource files" (included directly into apps) and "source files" separately, esp. given the Xcode restriction you've mentioned. Sometimes "sources" are identical to "resources" (there is no processing before app inclusion). In that case they should reside in "resources" directly or could be symlinked there (better for logical organisation of files and more future proof).

[rtsisyk]

What problem does this PR solve?

[AndrewShkrob]

mess in the data folder