Implement changes to Checks API for Annotations models and re-request endpoint

[ryangribble]

Fixes #1856

Attempt to handle both old and new annotations models so we can support github.com and GHE 2.14

• add Path and AnnotationLevel fields to CheckRunAnnotation response and NewCheckRunAnnotation request
• flag Filename and WarningLevel as deprecated/obsolete but keep them around so we can use them for GHE 2.14
• also flag BlobHref as deprecated on NewCheckRunAnnotation
• Adjust ctors so we have a way to create the "old" and "new" model formats, ensuring the relevant fields are null so they don't get sent
• Add new re-request endpoint
• Flag old request endpoint for deprecation

[ryangribble]

I think I've managed to get these changes done to support github.com and also leave the old models/methods intact to continue supporting GHE 2.14

@shiftkey @StanleyGoldman could you cast your 👀 over this just to double check? 🙏

[ryangribble]

release_notes: Implement new/changed fields on CheckRunAnnotation response and NewCheckRunAnnotation request models - replace Filename with Path, WarningLevel with AnnotationLevel and add StartColumn and EndColumn

[ryangribble]

advisories: Due to upstream breaking changes in the CheckRuns API, using check runs against github.com will require using the new/renamed fields on CheckRunAnnotation response and NewCheckRunAnnotation request models. However the old fields are maintained in octokit.net (marked as deprecated) to continue supporting GitHub Enterprise 2.14, which will not receive these changes. Users of GHE 2.14 should use the old fields, whilst users of github.com should update to use the new fields

[ryangribble]

release_notes: Add new method CheckSuitesClient.Rerequest() and mark the old CheckSuitesClient.Request() method as deprecated (this will no longer function on github.com but will continue to be supported on GitHub Enterprise 2.14)