Fix #12541: mc_issue_note_add function not honoring reporter data

When using the function mc_issue_note_add() the submitted reporter data aren't used.
This fixes allows users with 'webservice_specify_reporter_on_add_access_level_threshold'
access level to override reporter when submitting notes.  This makes it consistent
with mc_issue_add() api.
Document 'webservice_specify_reporter_...' config
Refactor override reporter access check

- Refactored the check in mc_issue_add() and mc_issue_note_add().
- Added TODOs to add the test cases to SOAP API when it is possible to add users via SOAP.