Revert of [stubs] Port KeyedLoadIC_Generic stub to TurboFan (patchset #4 id:60001 of https://codereview.chromium.org/2245683002/ )

Reason for revert:
Suspected to cause webgl_conformance_tests failures:

WebglConformance_conformance_textures_misc_tex_image_with_format_and_type (gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest) ... [21956:1299:0901/082859:INFO:CONSOLE(11)] "Uncaught TypeError: Cannot read property 'charCodeAt' of undefined", source:  (11)
[21956:1299:0901/082859:INFO:CONSOLE(174)] "Uncaught TypeError: Cannot read property 'charCodeAt' of undefined", source: http://127.0.0.1:56892/js/pnglib.js (174)

Original issue's description:
> [stubs] Port KeyedLoadIC_Generic stub to TurboFan
>
> And also handle dictionary elements loads in the dispatcher.
>
> Committed: https://crrev.com/fd5fe3b2a40cc7a9b044416798c3c2aa734469ff
> Cr-Commit-Position: refs/heads/master@{#39070}

TBR=verwaest@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2303793002
Cr-Commit-Position: refs/heads/master@{#39096}