[DSpace 8 Admin Reports] Performance issues caused by high number of item loadings.

[pilasou]

Is your feature request related to a problem? Please describe. DSpace 8 Reports cause performance load issues due to high numbers of item loading:

• See PR comment : https://github.com/DSpace/dspace-angular/pull/2163/files#r1452576823: Loading 1000 communities at once can cause bad performances. It put heavy strain on the backend, and also take a long time to parse and cache items on the front end. As the reports needs more collections than communities, maybe existing component that load collections in a paginated way can be reuse (ie.e ds-dso-selector or ds-collection-dropdown).
• See also PR Comment https://github.com/DSpace/dspace-angular/pull/2163/files#r1452578972: huge page-sizes should be avoided. In this case ds-metadata-field-selector may be reused to get a paginated dropdown of metadata fields