Perf tests for Template Literals

Review URL: https://codereview.chromium.org/769113002

Cr-Commit-Position: refs/heads/master@{#25789}
[turbofan] Various cleanups.

- Decouple JSBuiltinReducer from JSTypedLowering.
- Unify JSTypedLowering::ReduceJSToXXX() lowering.
- Cleanup several includes and forward declarations.
- Unify helper methods.

TEST=cctest
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/797903003

Cr-Commit-Position: refs/heads/master@{#25790}
Remove legacy python deps.

BUG=

Review URL: https://codereview.chromium.org/794113004

Cr-Commit-Position: refs/heads/master@{#25791}