[DPP] Fix usage of "DPP" public API to "Easy Connect"

All DPP public API and constants renamed to use Easy Connect,
which is the WFA public technology name. Update the settings code to use the
new API names.

Bug: 122851551
Test: atest DppManagerTest
Test: act.py -c ../WifiDppConfig.json -tc WifiDppTest
Change-Id: Ib531393a81526c468c978e31f1c62c5022245d55