Fix Maui.Controls.Sample Blazor dynamic root components trimming problem.

[MackinnonBuck]

Description of Change

Updated the Maui.Controls.Sample project to use the correct JSComponentConfigurationExtensions.RegisterForJavaScript() overload that permits adding root components via JavaScript in a linker-friendly manner.

Issues Fixed

Fixes #6965

[mattleibow]

Where does this "myDynamicRootComponentInitializer" value come from? Is it just app-specific and not used?

[MackinnonBuck]

@mattleibow Yes, it's just an identifier specific to the sample project. For this case, all we care about is that the correct overload of RegisterForJavaScript is called so the correct JS interop methods get linked in. That parameter generally represents an identifier of a JS function that gets invoked by Blazor to add the root component, but in this case, that function gets invoked by a button click. So we pass a unique dummy value instead so the root component doesn't get added when the page loads.

That said, I'm not completely sure what the original reasoning was for annotating this method overload for linker-friendliness, but not this one. If the latter were annotated, we wouldn't have to apply the change in this PR.

Offline, we've discussed annotating the TValue of DotNetObjectReference<TValue> with [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)], which should also make the first overload work again.

Assuming this is in fact a Blazor issue and not a misuse of RegisterForJavaScript in this sample project, we could close this PR and track the issue in a separate PR.

cc: @SteveSandersonMS @javiercn in case you have any thoughts about this.

[javiercn]

@MackinnonBuck Are we missing DynamicDependency on these two overloads? https://github.com/dotnet/aspnetcore/blob/c85baf8db0c72ae8e68643029d514b2e737c9fae/src/Components/Web/src/JSComponents/JSComponentConfigurationExtensions.cs#L25-L35

[eerhardt]

@javiercn - DynamicDependency attributes should only be used when you can't make it work with restructuring the code, or using DynamicallyAccessedMembers. See the warning at https://docs.microsoft.com/en-us/dotnet/core/deploying/trimming/prepare-libraries-for-trimming#dynamicdependency.

I have a PR to fix the underlying issue in ASP.NET with dotnet/aspnetcore#41610.

[mkArtakMSFT]

@eerhardt so no more concerns with this PR then ? Can we merge this ?

[MackinnonBuck]

Closing because dotnet/aspnetcore#41610 should fix the issue without requiring this change.