add changeable resolution as a parameter

[MichaelBrueggemann]

What

• add a parameter resolution to the process load_collection

Why

• this enables changing the spatial resolution of a datacube directly while creating it, rather than calling an additional process like resample_spatial later on. It's a "quality of life" feature, like selecting the "bands" in load_collection.

[PondiB]

@MichaelBrueggemann , Earlier implementation of openeocubes had this but I removed it as it was violating the processes as defined in openEO standard: https://processes.openeo.org/#load_collection

[PondiB]

Won't be openEO compliant