Fix some ArtMethod related bugs

Added root visiting for runtime methods, not currently required
since the GcRoots in these methods are null.

Added missing GetInterfaceMethodIfProxy in GetMethodLine, fixes
--trace run-tests 005, 044.

Fixed optimizing compiler bug where we used a normal stack location
instead of double on ARM64, this fixes the debuggable tests.

TODO: Fix JDWP tests.

Bug: 19264997

Change-Id: I7c55f69c61d1b45351fd0dc7185ffe5efad82bd3