Found while updating the feature spec for the feature. This article didn't clearly state that file local types are preferred over other types with the same name in the file where they are declared.

Also, the `file` modifier doesn't actually modify the *scope*, rather, it modifies the *visibility*. Update the language to match the speclet definition.

Finally, quick edit pass.

* Update notes on annotations

Update the article to use the language adopted by the C# standards committee to describe the nullable context, and the null state of any variables.

* freshness pass and bug fixes

Fixes #21941: Add description of the default values for arrays of reference types.
Fixes #30348: Edit pass
Fixes #33667:  Update the description of the nullable context to match the language used in the C# 8 draft standard
Fixes #36767: Add language on declaring a non-null array of nullable reference types and a nullable array of non-nullable reference types.

Also, perform a general edit pass.

* fix warnings

* Apply suggestions from code review

Co-authored-by: Andy (Steve) De George <[email protected]>

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Co-authored-by: Andy (Steve) De George <[email protected]>