Configure BannedApiAnalyzer through .editorconfig

**Brief description:**

Describe your **code style** rule here.
(The comment suggesting to add ` To propose a semantic/code quality analyzer, please follow the guidelines at https://github.com/dotnet/roslyn-analyzers/blob/main/GuidelinesForNewRules.md` is outdated since roslyn-analyzers is moved either here or to the SDK repo )

**Languages applicable:**

Is your analyzer C# only? VB Only? Or Both?
Not sure but I only care about C#

**Code example that the analyzer should report:**

Configuration in .editorconfig instead of a text file so we can consolidate analyzer configuration from there

**Additional information:**

N/A

**Documentation requirements:**

When this analyzer is implemented, it must be documented by following the steps at [Documentation for IDE CodeStyle analyzers](https://github.com/dotnet/roslyn/blob/main/docs/contributing/Documentation%20for%20IDE%20CodeStyle%20analyzers.md).

Start by reviewing BannedApiAnalyzer's existing text-file configuration and the requested .editorconfig approach. Clarify the C# configuration behavior and follow the documented steps for IDE CodeStyle analyzer documentation; done means analyzer settings can be consolidated in .editorconfig and the required documentation is updated.

Written by the indexing model from the issue text.