Remove connectivity dependency on Preconditions

Preconditions.checkNotNull is deprecated to be replaced by
Objects.requireNonNull, and other methods can easily be replaced by
inline checks.

Preconditions is an internal API class that should not be used by
unbundled jars.

Bug: 177046265
Test: m
Change-Id: If14a75439ff332c927dc4114ae0eecb89f53c6c7