[Sensor Product Import] add support for better sensor product management

[janzandr]

Discussed with @jakimowb.

Individual raster layers are currently managed in the Data Sources panel under the Rasters node. This works fine for already prepared reflectance data, like a Landsat/Sentinel-2 image, where the individual bands are already stacked together in one raster. Preparing such products, involves special Import Product algorithms, which prepare all the rasters related to a product and stored them as a new raster. E.g. for a PRISMA product:

After running the import algorithm, the prepared rasters are opened inside the Data Sources panel:

This is a pragmatic approach which works fine so far, but is not very convinient, because the user has to create new raster layers before product data can be used.

It is proposed to introduce a new concept for handling (sensor) products:

• a product can be opened without the need to directly import/prepare data
• the content of a product can be inspected in the GUI (associated raster, metadata, derived layer like bounding polygon etc.)
• indiviual raster can be opened easily in the EnMAP-Box (double-click or drag&drop)
  • Option A: use existing import algos to prepare raster layers (stacking, scaling, add metadata) [better not do this, because it involves the creation of new files]
  • Option B: implement a custom QgsRasterDataProvider for each sensor product, which serves the data on-demand by tapping into the original products; this would be optimal, but we need to get adding layer with custom QgsRasterDataProvider crashes QGIS qgis/QGIS#59284 fixed

Supported products:

• EnMAP
• PRISMA
• DESIS
• EMIT
• Landsat
• Sentinel-2
• Planet Scope

[janzandr]

Releated to #1008.