Formalize TelephonyManager EmergencyCallDiagnostic

Formalize the TelephonyManager#EmergencyCallDiagnosticParams API as part
of the Telecom modularization. This is only used by Telecom so
promote the existing functionality into a proper API.

Bug: 308472794
Bug: 311773409
Test: atest TelephonyManagerTest
Change-Id: I53c2f1e1d095cf6ab92cb8b551e67905dde525a3