_elements option should not be applied to the _include option on a search.

[d0roppe]

Describe the bug
A clear and concise description of what the bug is.
When issuing a search and specifying the _elements option to include specific elements only, it should not be applied to the resources returned due to the _include option. https://www.hl7.org/fhir/search.html#elements
Currently it is applied to all returned resources.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error
   Run a query with _elements=identifier&_include=:*

Expected behavior
A clear and concise description of what you expected to happen.

Additional context
Add any other context about the problem here.

[prb112]

#1494 should be tackled at the same time.

[d0roppe]

stretch goal for sprint 21

[d0roppe]

Verified that with this fix, the _elements is not applied to the included resources.