In this mode, each band in the raster can have a fixed elevation
range associated with it. This is designed for data sources which
expose elevation related data in bands, eg netcdf files, such
as a raster with temperate data at different ocean depths.
This introduces a new option for specifying how raster layers
have associated elevation. It permits a fixed elevation range
to be set for the layer. It can be used when the layer has
a single fixed elevation, or a range (slice) of elevation values.
Users can set the lower and upper elevation range for the layer,
and whether the lower or upper limits are inclusive or
exclusive.
When enabled, the layer will only be visible in elevation
filtered 2d maps when the layer's range is included in the map's
z range.
These flags reflect that retrieval of the provider's 2D or 3D extent
retrieval via QgsDataProvider::extent()/extent3D() are ALWAYS guaranteed
to be trivial/fast to calculate and involve absolutely no extra work.
