Revert^2: Spawn background verification for InMemoryDexClassLoader

After dex files have been loaded with InMemoryDexClassLoader, call
DexFile.verifyInBackground which instructs ART to spawn a background
thread and verify all newly loaded classes. This thread will be used
for creating a vdex file to speed up subsequent loads of the same
bytecode.

This reverts commit f501b122.

Bug: 72131483
Change-Id: I46cd8f854642ff3d30d3b595ffa035aeb6f2c8ec
Test: art/tools/run-libcore-tests.sh
Test: art/test.py -b -r -t 692