Fix nullness errors reported by Eclipse

Eclipse provides a lot of noise around builders where we pass
down classes. This fixes them up by losening the contracts and
adding Class<@NonNull T> where generics are involved. Since we are
at it, also fixup the suite to generate fewer warnings.

JIRA: MDSAL-601
Change-Id: I7b21d88584a18cc1bed6ea776b22e82584484339
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>
(cherry picked from commit 1fcf6b07a764c57aff7435cffd620c4995d1db40)