Introduce formatting and analyzers

[kfcampbell]

This project already has an .editorconfig courtesty of #15. This PR adds a CI check and a script that can be used locally, both of which call dotnet format to ensure our source files are compliant with the .editorconfig.

[github-actions]

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[kfcampbell]

Hmm...I had set this up to use https://github.com/dotnet/code-analysis, but that repository hasn't been updated in 3 years and does not run on .NET 8. I believe it to be abandoned and I don't want to run on a super old version of .NET just to use an old analysis tool.

Instead, I'll focus on using the built-in Roslyn analyzers.

[kfcampbell]

I've implemented the following snippet in our .csproj files:

    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
    <EnableNETAnalyzers>true</EnableNETAnalyzers>
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
    <!-- The below NoWarn is due to Kiota generating code marked as Obsolete.
      This is expected, but we still want to error on other warnings from analyzers. -->
    <NoWarn>$(NoWarn);CS0618</NoWarn>

This explicltly enables .NET analyzers (though they're on by default because we use .NET 8) and treats warnings as errors. I've ignored all CS0618 "Obsolete" errors since Kiota expectedly generates some code with "Obsolete" modifiers.

Together with our CodeQL analysis Action, this should cover all necessary linting pieces for our dotnet-sdk.