Use `PushFilePreparer` to push files in PreloadCheck

This change modifies the test config file by switching to use `PushFilePreparer` instead of `FilePusher`, since the `FilePusher` class which is defined in `compatibility-tradefed` is designed for the tests that are part of compatibility suite, but PreloadCheck is not.

Bug: 220991354
Test: atest PreloadCheck
Change-Id: Id25a16d6339b0ec8b5b61f1799c842f5ebd143ba