Update metadatablock logic to fail if dataverse collection does not exist

[scolapasta]

When uploading a metadatablock via tsv file, you can specify a dataverse collection (when you do, that block is only available in the subtree of the installation).

Currently, if you do this and the dataverse collection does not exist, the upload succeeds with the block being universally available. This issue is a suggestion to change the behavior, so it fails in this case.

[poikilotherm]

Just a heads up that #7662 will contain a new parser for TSV file validation and Solr schema creation. This will not include validation for existence of a collection of course...

I dunno if the parser might be a thing for a refactoring when touching this code.