fix: datasets ordered by dates created

[vfried]

There was a bug in dataset search that was not ordering datasets per imported date.

I revised the way we handle dates in datasets to display it in a more accurate way.

Datasets Search
We get from the KG "date" we check if the dataset was published or not (we do this by checking if it has a datePublished or not) we display "Published date" or "Created date" and the date.

Dataset Display
For datasets inside projects:

• Datasets created in renku: Inside projects we get created_at from the core service we map this to created
• Imported datasets: we get datePublished from the KG and we use this since we get nothing from core

For datasets inside the kg (display from search)

• Datasets created in renku have created
• Imported datasets have published date

For datasets that are not in the KG(only inside projects):
We only get a date_created for datasets created in the KG so we display this (we map it to created)

Closes #1226

/deploy

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-ui-1240.dev.renku.ch

[lorenzo-cavazzi]

Works as advertised 👍

[RenkuBot]

Tearing down the temporary RenkuLab deplyoment for this PR.