Fix free text basic search post

[fmigneault]

Related Issue(s):

• fix type for advanced freetext and allow free-text for Item search #263

Description:

When POST /search is used with basic free-text, the q: list[str] format was not being transformed to ... OR ... format as in the case of collection search.

By moving the cleanup within _clean_search_args, the POST /collections/{id}/items and POST /collections endpoints are also fixed for q parameter (assuming transaction extension is not active).

PR Checklist:

• pre-commit hooks pass locally
• Tests pass (run make test)
• Documentation has been updated to reflect changes, if applicable, and docs build successfully (run make docs)
• Changes are added to the CHANGELOG.