[REF] extract buildGroupTree function

[eileenmcnaughton]

Overview

Function extraction

Before

Less readable

After

More readable

Technical Details

I did this mainly to surface the fact that the variables involved are factored into the cachekey for
#14292

Comments

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[colemanw]

I feel like this extraction could be cleaned up a little so it doesn't have to take so many variables, but I don't want to bog this down with nitpicking. For now how about just making the new function private so future generations can refactor it with confidence.

[eileenmcnaughton]

@colemanw good call - done

[eileenmcnaughton]

test this please