... and add explicit CallPrologue/CallEpilogue callbacks to CodeAssemblerState instead.
This will allow IntepreterAssembler to use any other helper assembler.

TBR=rmcilroy@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2600183004
Cr-Commit-Position: refs/heads/master@{#41973}