Introduce CompanionSecureCommunicationsManager

Add com.android.server.companion.securechannel and the outline for the
CompanionSecureCommunicationsManager class.

Bug: 202926196
Bug: 198485833
Test: atest CtsCompanionDeviceManagerCoreTestCases
Ignore-AOSP-First: new OWNERS file (not yet in AOSP)
Change-Id: I7c4d88e65430d31332df69d0d9e6b087c2805df6