port 7877c4e0 (r29814).

original commit message:

    Adds basic support for generation of interpreter bytecode handler code
    snippets. The InterpreterAssembler class exposes a set of low level,
    interpreter specific operations which can be used to build a Turbofan
    graph. The Interpreter class generates a bytecode handler snippet for
    each bytecode by assembling operations using an InterpreterAssembler.

    Currently only two simple bytecodes are supported: LoadLiteral0 and Return.

BUG=

Review URL: https://codereview.chromium.org/1256783002

Cr-Commit-Position: refs/heads/master@{#29838}