[Scicat Widget] Add pagination / infinite scroll / filter to dataset select

[omkar-ethz]

Currently, only the 100 most recent datasets are fetched in the select dropdown in SciCat Viewer widget.

Proposed state: in the widget configuration, pre-select a dataset based on proposal ID, and give an option to select any other dataset with the possibility to filter based on dataset name / keyword. Implement infinite scroll / pagination to let the user go through all accessible datasets.