passpoint-r2: handle multiple CA certificates

This is required to save the AAA root CA certs for PPS MO.
Put @hide for new API because this is only used for wifi service.

Bug: 117717842
Test: ./frameworks/base/wifi/tests/runtests.sh
Test: tested with R1 AP for installing profile and R2 AP for connection
Change-Id: Ib84c030024d3429140cd80bb622fd23ca608b9bb
Signed-off-by: Ecco Park <eccopark@google.com>