[Turbofan] Macro-ize instruction selection for x64.

- Uses macros to reduce code duplication.
- Uses calls to VisitRO and VisitRR to reduce code bloat.

LOG=N
BUG=v8:4124

Review-Url: https://codereview.chromium.org/2668753004
Cr-Original-Commit-Position: refs/heads/master@{#42828}
Committed: https://chromium.googlesource.com/v8/v8/+/e8e2e3c826d42490f809e1c45750bbb438b60d8c
Review-Url: https://codereview.chromium.org/2668753004
Cr-Commit-Position: refs/heads/master@{#42862}