binder_parcel_fuzzer: readEnumVector

These methods were added recently. We can't fuzz them actively because
of b/131868573, but adding them here so that they aren't forgotten.

Fixes: 141999100
Test: run test a few times with these enabled,
    hit oom (didn't hit anything else)

Change-Id: I1dc65b47201f5953fb02269cf421b1f52de306df