consolidate multiple external tools on cc import

test plan:
* import the common cartridge package referenced in
 the ticket and other common cartridge packages with
 external tools
* instead of having many copies of an external tool
 with the same settings and domain, merge them together into
 one
* each module item should still work with their individual url
and config, even though they're pointing to the same external tool

fixes #CNVS-13144

Change-Id: Idabe9ac95ea0605feb6dd9121a171b5e45e05a2e
Reviewed-on: https://gerrit.instructure.com/35193
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Reviewed-by: Brad Humphrey <brad@instructure.com>
Product-Review: Bracken Mosbacker <bracken@instructure.com>