carrier-config: define imsi_eap_identity_sequence_int key

Some of Carrier Wi-Fi Networks doesn't support receiving encrypted-IMSI
as EAP-RESPONSE/IDENTITY due to network deployment architecture.

So, a new key is required to define a sequence of sending encrypted-IMSI
identity during EAP-SIM/AKA authentication.
If this value is 2, anonymous@<realm> will be sent as a
EAP-RESPONSE/IDENTITY first and followd by
encrypted IMSI as EAP-RESPONSE/AKA|SIM-IDENTITY.
1: encrypted-IMSI (default one)
2: anonymous -> encrypted-IMSI.

Bug: 109795427
Test: manual
Change-Id: I1121f21b771707ed7c8350826cefc43445f4fc8b
Signed-off-by: Ecco Park <eccopark@google.com>