Thus TypeFeedbackMetadata can now be shared between different native contexts.

Review URL: https://codereview.chromium.org/1384673002

Cr-Commit-Position: refs/heads/master@{#31143}

This CL also allows to use arbitrary number of feedback vector elements for particular slot kind.

Review URL: https://codereview.chromium.org/1370303004

Cr-Commit-Position: refs/heads/master@{#31050}