Fix: Rescale vector tiles depending on dpi in print

[sweco-seguro]

The olms extension now rescales mapbox vector tiles when changing the dpi of a print.

The extension creates one style for each configured print resolution, which is then applied when said print resolution is chosen.

Fix for #1801

[jokd]

Unable to test this but it looks good so I suggest we merge it

[Grammostola]

There are one or two changes incoming

[Grammostola]

There's a minor niggle with an error when the print preview exits, a default param is given a null value, else it looks good.

There are two potential discussion points:

• The Olms extension now takes a config object with a possible list of resolutions in the case that the print has somehow been initialized with different resolutions than the current ones (75, 150, 300).
• The fill-pattern paint prop for polygons can look slightly funny at 75 and 300 dpi. Not "obviously wrong" that I've seen but not optimal always either. The prop can acc to the spec refer to a raster (not a vector graphic, I asked the mapbox style spec resident AI) in the spritesheet or another image. https://docs.mapbox.com/style-spec/reference/layers/#paint-fill-fill-pattern . With "spritezero" a spritesheet can be created from .svg-graphics for hiDPI displays and standard displays and ol-mapbox-style I'd guess detect the display and apply the "2x" sprite sheet or the normal one. Inside one sprite sheet there can be several rules with several different raster images for the same layer at different zoom levels. "Different print dpis" isn't so much a concept unless we choose to apply it, that is to say make the print control suppose style rules with a distinct print-dpi-related name and those rules and images would need to be in (each) style sheet.