Make *Cached* benchmarks actually use cached objects.
Make *Cached* benchmarks actually use cached objects.

Change-Id: I35225a64456373269513dcd47e1f97517dd34777
Reviewed-on: https://code-review.googlesource.com/c/re2/+/58290
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

google/re2,google/re2,google/re2,google/re2,google/re2