Replace WebAssembly Hot Reload code with Microsoft.DotNet.HotReload.Agent.nupkg

[danroth27]

• ✅ Replace Components/WebAssembly/WebAssembly/src/HotReload with Microsoft.DotNet.HotReload.Agent.nupkg from the dotnet/sdk repo.
• Ensure the implementation works for .NET WebAssembly scenarios. Where there are mismatches, update the source package to benefit all workloads.
• Ensure the integration tests validate the complete system works as expected.
• In the future, there will be periodic updates to the shared packages. The integration tests will make it as simple as possible to identify and diagnose potential issues.
• Testing tracked in [Blazor] Hot reload testing improvements #59450

[javiercn]

@maraf what's remaining here?

[maraf]

Blazor is already using the source package produced by SDK. I'm working on second part of extracting everything hot-reload specific to a proper package, that can be referenced by any WebAssembly-based app.