Refactor quick entrypoints

Remove FinishCalleeSaveFrameSetup.
Assembly routines write down anchor into TLS as well as placing runtime
method in callee save frame.
Simplify artSet64InstanceFromCode by not computing the referrer from the
stack in the C++ code.
Move assembly offset tests next to constant declaration and tidy arch_test.

Change-Id: Iededeebc05e54a1e2bb7bb3572b8ba012cffa1c8