Allow all types of files to be passed as dex files.

In fact, dex2oat doesn't have a limit on the file extension. It only
checks the magic number at the beginning of the file. Potentially, apps
can use any extension for their secondary dex files.

Bug: 272053358
Test: Presubmit (v2/android-app-compat-engprod/csuite/top_100_app_launch_presubmit_partition_1)
Ignore-AOSP-First: ART Services
Change-Id: I933344f3b3b6d3dca23ca97f2846aff7f0aa2ba1