Revert^2 Verify InMemoryDexClassLoader classes in a background thread

When dex bytecode is loaded using InMemoryDexClassLoader, automatically
spawn a background thread which performs bytecode verification on every
class.

This reverts commit b4bb63aa. This CL
fixes a previous issue where runtime threads are not allowed to load
classes in debuggable mode.

Bug: 72131483
Change-Id: Icdeb5be2b33ef55675e3a23886e71ce3b4b02f43
Test: art/tools/run-libcore-tests.sh
Test: art/test.py -b -r -t 692