Clean up `ResetOffset()` calls in profile tests.

Most are unnecessary since
    https://android-review.googlesource.com/1685637
and we remove a few more by using `PreadFully()` instead
of `ReadFully()`.

Test: m test-art-host-gtest
Bug: 148067697
Change-Id: Ia654f4519ea9ca91f9a5ca26af55899ccdf4bb78
2 files changed