Fix kotlin nullable errors in perftests

Fix kotlin nullable errors that were exposed by setting the retention
of android.annotation.NonNull and android.annotation.Nullable to
class retention.

Bug: 294110802
Test: builds
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:2522501d5b4b4eab8d20986aa1c4b6ed36640211)
Merged-In: Icfec5d0e20b534d7af9aeb1b539a711db76d5e5c
Change-Id: Icfec5d0e20b534d7af9aeb1b539a711db76d5e5c