refactor: use file scoped namespaces

[JamieMagee]

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-10.0/file-scoped-namespaces

These changes were made automatically by my IDE. I recommend reviewing with whitespace changes off.

[JamieMagee]

Test failure is due to snapshot difference on Ubuntu, and will be fixed in #399

[github-actions]

👋 Hi! It looks like you modified some files in the Detectors folder.
You may need to bump the detector versions if any of the following scenarios apply:

• The detector detects more or fewer components than before
• The detector generates different parent/child graph relationships than before
• The detector generates different devDependencies values than before

If none of the above scenarios apply, feel free to ignore this comment 🙂

[JamieMagee]

I'll follow this PR up with another one to add a .git-blame-ignore-revs file, so git blame doesn't become useless

References:

• https://github.blog/changelog/2022-03-24-ignore-commits-in-the-blame-view-beta/