Add Sarif output support to FSharpLint.Console

[Numpsy]

refs #554

I've recently been having a go at running some things at work through the FSharp.Analyzers.SDK analysis tools and pushing the generated Sarif report files into DevOps CI builds, and I thought it might be useful to see if I could get FSharpLint results pushed out in the same way - so, this is a first attempt at adding Sarif report generation into FSharpLint.Console.

Note: The Sarif writer code is currently a lightly modified version of the report code from https://github.com/ionide/FSharp.Analyzers.SDK just to try to get it working, so if the code style and such is wrong that's the reason.

[Numpsy]

It might also be possible to make it generate a sarif report from the SelfCheck runs in CI builds and push that into the Github code analysis integration, e.g. as done in FsAutoComplete:
https://github.com/fsharp/FsAutoComplete/blob/7d2d2ec851392fb7ed08b520a1be7782f24eb3be/.github/workflows/build.yml#L127

[Numpsy]

Rebased on top of the latest code (The Paket changes are gone now, so previous comments about that don't apply any more

[xperiandri]

Looks good, use object initializers, please

[Numpsy]

Rebased to fix conflicts, haven't got to the other comments yet.

[xperiandri]

Resolves #554

[Numpsy]

If there aren't different levels for different rules, should the default here be Warning or Note?

[Numpsy]

Any other comments on the general idea?
(It'll need some documentation somewhere, but I want to get the idea checked before spending time on that)