Associate an originator identity to sessions

This change formalizes the permission enforcement patterns in the
sound trigger middleware layer. Every sound trigger session is
associated with an originator identity, established during attachment.
This identity is the used to authorize any operations performed on
this session, including data deliver via callbacks.

Temporarily, for b/w compatibility the existing SoundTrigger.java API
is preserved. Follow up changes will use the newer API, which requires
an identity to be provided.

Logging / dumpsys aspects have been modified to include the originator
identity associated with every call / session.

Change-Id: If83b151bd182af5a0dd98ff23dce252018de936b
Bug: 163865561