chart: extend configurability - full datasets

Current chart allows mapping tilesets to sources 1:1, taking LAYER ID and possibly STYLE parameter as a LAYER to ask from renderer per tileset.

Our vhr18 mapcache configuration https://gitlab.eox.at/esa/prism/vs/-/blob/staging/config/vhr18/vhr18_mapcache-ops.xml#L64 is more complicated with having custom _full tilesets without time dimension and not being 1:1 mapping. Additionally there are two buckets used: vhr18_cache and vhr18_cache_full, but that could be solved now by migrating the data in operations.

Therefore creating vhr18 config from the chart now is not possible.