Use the right class loader allocator in ReallocMethods.

Otherwise we would leak memory.

Also complies with the JitCodeCache assumption that ArtMethods
are allocated with the classloader that loaded the class where
those ArtMethods hang.

bug: 64241268
Test: 661-classloader-allocator

(cherry picked from commit 48b40cc9)

Change-Id: Ifd8f2cf5dc5f4557dda1cca4b9e5764a67571f88