Stop exposing reasons through phone state listener

The data connection reasons are implementation details
of telephony and should not be exposed externally. The
data connection fail cause, which is different from
reasons, are still available.

Test: Telephony sanity tests + unit tests
Bug: 73659459

Merged-In: Ia005abf19664e6213118ee932495950af118456d
Change-Id: Ia005abf19664e6213118ee932495950af118456d
(cherry picked from commit 4d1c9450)