Clean up generation of NetAnalyzers GenerateAnalyzerRulesMissingDocumentationFile stuff

### Is your feature request related to a problem? Please describe.

With https://github.com/dotnet/sdk/pull/50167 added to the repo the build now creates a new file that's constantly being generated on many different PRs from the GenerateAnalyzerConfigAndDocumentationFiles Target.

This file needs some other generation strategy - the Target itself isn't incremental (in the MSBuild sense), it gets constantly regenerated on every build (which the SDK team does _frequently_ to run tests, test new layouts, etc), and generally makes me a very sad panda.

### Describe the solution you'd like

If this file is required, it should be
* generated to a location that doesn't show as an untracked file to everyone working on the SDK
* the generation of the should ideally be incremental
* there should be some sort of guidance/check that can flag this file for follow-up by the net analyzers owners, etc.
* not generate noise in the day-to-day of the SDK repo