Update Xref Gen tool

[guardrex]

Addresses dotnet/AspNetCore.Docs#34461
Addresses dotnet/AspNetCore.Docs#34107

[guardrex]

@Rick-Anderson @wadepickett @tdykstra @danroth27 @lewing

Looking good with the latest code for the Blazor WASM-based Xref Gen tool hosted on GH Pages ...

https://dotnet.github.io/blazor-samples/

It's using a different, hopefully more reliable approach, to get the XREF links now.

In the prior versions of the tool, it would take the display name from the .NET API Browser's web API backend and manually try to construct the same value as one sees in the API Browser page's ms.assetid meta tag value. That was a pain point and a little hard to do.

Now, it takes the URL that the API sends back, makes a CORS proxy request for the API Browser webpage, and Regex-parses the value of the ms.assetid <meta> tag. This should work well, as long as we don't hit some kind of request limit with the CORS proxy that I went with (https://corsproxy.io) and CloudFlare is OK with this being a permanently "in development" tool. What I might end up doing is figuring out something more robust via a subscription with CloudFlare, using one of the other CORS proxies, or setting up my own Azure-based proxy.

Anyway ... you can use it now and let me know about any bugs by opening an issue on this repo. I'll probably work on it a bit more tomorrow (e.g., it's wired specifically to aspnetcore-9.0 right now, but that could be from a DDL in the UI).