ClassicPairingHandler: Add Out of Band support.

Adds support for p192, p256, and both.  As well as
secure connections "extended data" versions of the
RemoteOobDataRequestReply.

Add several unit tests to verify the pairing handler
correctly behaves.

Bug: 162984360
Tag: #gd-refactor
Test: cert/run --host SecurityTest
Test: atest --host bluetooth_test_gd -- --test-arg com.android.tradefed.testtype.GTest:native-test-flag:--gtest_filter=ClassicPairingHandlerTest*
Change-Id: I72016f380a29ad11ec9bdd9e0dcb3383c092c830