[wpa_supplicant] Read certificates from keystore in DER format

Read Root CA and user certificates from keystore in DER format.
Only if it fails, try to use PEM format for backward
compatibility.

Bug: 184298873
Test: Connect to Wi-Fi networks with EAP-TLS and EAP-TTLS and
verify logs.

Change-Id: I599e55485a89b2d18e29df0f347cfe4c1d9dba15
2 files changed