Add flag btsec_le_oob_pairing

Test: m libbluetooth
Bug: 374376990
Bug: 315241296
Flag: com.android.bluetooth.flags.btsec_le_oob_pairing
Ignore-AOSP-First: security
Tag: #security
Change-Id: Ie35bb3daa7a52fe54ef96a5eec25535afe7214aa