Add parsing of raster symbology

[bogind]

This has been a sore point for a while now, users asking for at least minimal support for raster styling.

As there can be multiple CIM layer types who are considered "raster", it might be better to refactor the current way qlyrxStyler.apply_lyrx_symbols identifies symbology types isn't suited for use with raster layers (including raster image/tile/elevation services) as they do not have a renderer attribute - see CIMRasterLayer Class Members.

TODO:

Globally:

• Checking each layerDefinition's type attribute should be the first step in applying symbology, to identify unsupported layer types. see list of layer types under the CIMBaseLayer Class
• low priority - apply LayerElevation for all layer types. Useful for all layer types, but might be more important in rasters, elevation models in particular.
• Move messaging to styler or other sub-modules, currently reporting success in cases where exceptions are caught or styles are not supported

For Rasters:

• identify and apply Colorizer
• identify and apply BlendingMode

There are likely other relevant attributes, but these are a good place to start