[Blazor] Investigate why E2E tests aren't catching trimming issues

[MackinnonBuck]

We should ensure that Blazor's E2E tests are running against published/trimmed versions of each test app. We've had a few trimming issues that had to be caught manually (e.g., #56333, #53746, #51665).

[MackinnonBuck]

I did some investigation here and it does look like our E2E tests catch glaring trimming issues.

The challenge with catching more subtle trimming problems is primarily that since the test app (BasicTestApp) is so big, it's more likely to reference code that would otherwise get trimmed out on a smaller app (e.g., a new project).

Thankfully, as of #54606, we are now getting coverage for projects generated from our project templates, and these tests validate that trimmed, published apps work correctly (the counter can be clicked, etc.). I introduced a trimming issue locally to determine if the template tests would catch it, and they did.

Closing this out now as there doesn't seem to be anything more to do here.