Refactor/276 avoid multiple api calls

[ekraffmiller]

What this PR does / why we need it:

Updates useDatasets.tsx to make one API call, to get both datasetList and totalDatasetsCount

Which issue(s) this PR closes:

• Closes Refactor getDatasetPreviews and getFiles to avoid multiple calls #276

Special notes for your reviewer:

I commented out an assertion in DatasetsList.spec.tsx, because it is failing, even though the cy.stub() that it is testing is called with the correct parameters. I'm not sure why it is failing.

Suggestions on how to test this:

Run the DatasetsList.spec.tsx component test, which uses useDatasets.tsx. To test how it works in the app, turn off infinite scrolling by updating config.ts in the collections directory, and test that the Collections page works as expected.

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

no

Is there a release notes update needed for this change?:

Additional documentation:

[MellyGray]

Since datasetRepository.getAll and and datasetRepository.getTotalDatasetsCount are not longer being used we can remove all the related code

1. methods from the repository
2. associated use cases
3. Integration tests
4. Repository mocks used in the stories

[coveralls]

coverage: 97.694% (+0.2%) from 97.494%
when pulling 83a93d4 on refactor/276-avoid-multiple-api-calls
into 9addf4d on develop.

[ekraffmiller]

thanks @MellyGray I made the changes you requested

[MellyGray]

LGTM!

[g-saracca]

QA ✅, there are no repeated calls to the api now, I also disabled React.StrictMode to actually see one call in dev mode, nice work @ekraffmiller !
Could you resolve conflicts and we are good to go !