Blazor VSC launch/tasks/debug guidance updates

[guardrex]

Fixes #22234

Thanks @samcarey! #22325

Notes:

• It's challenging to cover cleanly because there are permutations of hosting (standalone vs. hosted), some sort of 🐞 bug in VSC launch.json/task.json automatic config, stock launch/task setup (non-debugging) vs. launch/task setup with debugging.
• I think what I've worked out covers things, and we can take feedback on this to see if further confusion 😵 ensues.
• Because I favor adding the .vscode assets to a hosted WASM app's solution folder, I don't think we should keep the old Launch and debug a hosted Blazor WebAssembly app with Microsoft Edge section, so I delete it here. That's now covered by the new content added on this PR. By opening at the solution level, all of the solutions folders/projects (Client, Server, and Shared) are visible to the user. When run from the solution's folder, it runs the Server project. That's what I prefer to do anyway in my own use of VSC with hosted WASM.
• My local test of this guidance was successful using the Blazor-SignalR tutorial hosted WASM solution. I 🙈 RexHacked!™ 🙈 my way to the coverage on this PR. I'm able to set and hit breakpoints client- and server-side. However, I'm a little concerned about this being correct and stable. 👀👂
• I haven't reached the Blazor WASM Debugging topic yet on the UE passes, so I'll get another shot at updates when it comes up for general work.
• Disregard the build failure: It's a false positive for this PR. We'll merge past it after review+updates+approval.

[guardrex]

@Rick-Anderson ... I thought you killed off the Cyberdine Systems Snippet Builder 5000™???

— I'm back. Cyberdyne Systems T-800 Series Model 101 (Arnold Schwarzenegger)
     Terminator 3: The Rise of the Machines ©2003 Skydance Media

[Rick-Anderson]

@guardrex I'll be back
That's something different and unrelated.

[guardrex]

Oh, I see. I thought those two were related. This is just a failure on warnings but that leave the PR mergable. Got it! 👍

[captainsafia]

Looks good!

Re: the other thread. There's been some churn in the VS Code extension recently so I'll try and repro some of this stuff. We've been changing some of the codepaths related to detecting Blazor projects.

[guardrex]

@captainsafia Very well ... I merged your heading update and will get this live.

I'll circle back around on the UE passes to the WASM debug topic for a general edit and another look at how these use cases compose. The permutations of use cases are a bit tricky to work out 😅.