Revert^2 "Ensure that methods requiring interpreter entrypoint always have it."

The code in test 067-preemptive-unpark is able to cause a method to
have a null entrypoint. This is a valid (though rare) state. The check
we had did not account for it and failed. Made the DCHECK explicitly
allow for null entrypoints.

This makes the check consistent with the code around lines 363 and 398
lower in the function.

This reverts commit c971f6e0.

Reason for revert: fixed issue causing test 067 and others to fail.

Test: ./test.py --host -j50
Test: ./test/testrunner/testrunner.py -j50 -t 067-preemptive-unpark

Bug: 62821960

Change-Id: I537e05fd52fa4c8859d4102ac9475cacd75d7437