Add foreign implementation for push

[i-am-the-slime]

Avoid array allocation for push

The previous implementation would create a new array every time
This one is a pretty faithful call into JS's push.

Supersedes #237 and closes #236

Checklist:

• Added the change to the changelog's "Unreleased" section with a reference to this PR (e.g. "- Made a change (#0000)")
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation
• Added a test for the contribution (if applicable)