Make the BlockSuppressionStatus constructor

As per API feedback, this CL makes the BlockSuppressionStatus
constructor package-private as it's only referenced by
BlockedNumbersManager#getBlockSuppressionStatus.

Bug: 384813637
Flag: EXEMPT update existing API
Test: atest BlockedNumberContractTest
Change-Id: I3165310b2d14d1eb351eff053df4f1ffdfa6b199