Add access flag for previously warm methods

We want to know if the method was warm instead of just having a non
zero counter. This is required if we want to not compile all of the
startup methods, but still compile warm methods.

Test: test-art-host ART_TEST_JIT=true

Bug: 62200509

Change-Id: I6e04866f39f970b04b47342b7af5ed474e1f4172