Mostly by avoiding unnecessary Handle/HandleScope creation,
"length" property lookups, and length conversions.
This yields about 60% speedup on the microbenchmark I tested with.

Note that the C++ builtin is the middle performance tier of three,
so not every Array.push use case will be affected by this patch.

Review URL: https://codereview.chromium.org/1716833002

Cr-Commit-Position: refs/heads/master@{#34268}