Loosen restrictions on CheckedNumeric bitwise operators

Allow any integer types but always promote the result to unsigned.
This is more consistent with how these operations are normally used.

NOTRY=true

Review-Url: https://codereview.chromium.org/2529413002
Cr-Commit-Position: refs/heads/master@{#434859}
3 files changed