Add 1 person override GitHub action

[normj]

Description of changes:
To cut down the boiler plate time for smaller PR we want to experiment with allowing small PRs to opt-in to reducing reviewer approval to 1 person. By default 2 people will still be required unless the 1p-approval label is applied by somebody with write or admin permissions.

The PR adds the GitHub action that will enforce that 2 people with write or admin access has approved the PR. After this PR is merged we'll change the GitHub settings to reduce the required approval count to 1 and create the 1p-approval label.

The action works by running on new PRs being changed or labels applied or removed. It will fail if there are not 2 approvals or 1 approval and the 1p-approval label is not applied.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[boblodgett]

The description doesn't sound correct so I am trying to determine actual intent:

After this PR is merged we'll change the GitHub settings to reduce the required approval count to 1 and create the 1p-approval label.

Why would we need 1p-approval if we are reducing the require approval count to 1. You would need a 2p-approval label if reducing the rules. Or are the required approvals staying at 2?