Fix object page ignoring the filters for JSON and CSV export

[Donnype]

Changes

I added a test for this and used the queryset instead of another connector.list().

Issue link

Closes #1095

Proof

See test

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Code Checklist

• All the commits in this PR are properly PGP-signed and verified;
• This PR only contains functionality relevant to the issue; tickets have been created for newly discovered issues.
• I have written unit tests for the changes or fixes I made.
• For any non-trivial functionality, I have added integration and/or end-to-end tests.
• I have performed a self-review of my code and refactored it to the best of my abilities.

Communication

• I have informed others of any required .env changes files if required and changed the .env-dist accordingly.
• I have made corresponding changes to the documentation, if necessary.

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Checklist for code reviewers:

Copy-paste the checklist from the docs/source/templates folder into your comment.

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Checklist for QA:

Copy-paste the checklist from the docs/source/templates folder into your comment.

[ammar92]

Nice one, great test

[Darwinkel]

Checklist for QA:

• I have checked out this branch, and successfully ran a fresh make reset.
• I confirmed that there are no unintended functional regressions in this branch:
  • I have managed to pass the onboarding flow
  • Objects and Findings are created properly
  • Tasks are created and completed properly
• I confirmed that the PR's advertised feature or hotfix works as intended.

What works:

• Both CSV and JSON exports obey the (various combinations of) the search filters.
• No apparent regressions

Bug or feature?:

• Minor nitpick: the JSON and CSV exports do always state filters: All, which is presumably not the case ;)
  If it's an easy fix, then it would be nice to change this.