Switch cc field on emailTrait to use entity reference

[eileenmcnaughton]

Overview

Extend #17064 to cc field

Before

cc field uses custom js

After

cc field uses entity reference

Technical Details

Per #17064 - note this only affects the cc field - I have left the to field for now as it will be a bigger code cleanup

Comments

@colemanw

[civibot]

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[colemanw]

Tested this out and it works great. Nice to see more code removal.
Can't wait for the "To:" field followup and how much code gets deleted there!