REST resource API rate limit information

[lizkenyon]

When using the REST resources there is currently no way to access the rate limit information

Description

Fixes #1218

Please, include a summary of what the PR is for: Commit for adding resources

• This PR adds two nilable variables to the resources
• api_call_limit which is a hash with the header information from X-Shopify-Shop-Api-Call-Limit
• retry_request_after which is the header information from Retry-After

Commit for fixing flacky test

With this PR we uncovered several flaky tests, because to of the way they were updating context. We went with the easiest solution for now and set the context back to original after the test completes.

Commit for regenerating REST resources

Because some tests in the test suite use real resources instead of FakeResource we need to regenerate the REST resources to have the new variables for them to pass.

Commit for Docs

• There are some failing test right now due to core changes. I am working with the internal teams to get those updated.

How has this been tested?

Please, describe the tests that you ran to verify your changes.

Checklist:

• [ ] My commit message follow the pattern described in here
• [ ] I have performed a self-review of my own code.
• [ ] I have added tests that prove my fix is effective or that my feature works.
• [ ] I have updated the project documentation.
• [ ] I have added a changelog line.