Remove await for WASM platform.callEntryPoint

[TanayParikh]

Description

Regression introduced via: #31769

• On Blazor Server, Blazor.start returns a promise that resolves when the .NET code starts up and the app becomes interactive
• On WebAssembly:
  • Prior to Remove Entrypoint Invoker #31769, Blazor.start behaves the same as server (the promise resolves when the app becomes interactive)
  • Since Remove Entrypoint Invoker #31769, Blazor.start returns a promise that doesn’t resolve until the .NET app exits, which typically means never, and hence prevents its usage for triggering post-.NET startup logic

This PR is meant to revert that specific bit of logic, so that we no longer await the platform.callEntryPoint function and thus Blazor.start returns a promise that resolves when the .NET code starts up and the app becomes interactive. This now matches the behavior from 6.0-preview3.

Customer Impact

Without this PR we inadvertently introduce a breaking change where the Blazor.start promise doesn't resolve until the .NET app exits. This prevents its usage for triggering post-.NET startup logic.

Regression?

• Yes
• No

[If yes, specify the version the behavior has regressed from]:

Regression from 6.0-preview3
Regressed by: #31769

Risk

• High
• Medium
• Low

[Justify the selection above]
Returning the await logic to what it was prior to #31769 which was introduced in Preview 4.

Verification

• Manual (required)
• Automated: Remove await for WASM platform.callEntryPoint #31997

Packaging changes reviewed?

• Yes
• No
• N/A

Addresses #31971

[ghost]

Hello human! Please make sure you've included the Shiproom Template in a comment or (preferably) the PR description. Also, make sure this PR is not marked as a draft and is ready-to-merge.

[pranavkm]

Changes look fine. As part of merging this in to main, could we add a test for this? I was under the impression that we had end-to-end coverage for all of the startup behavior.

[SteveSandersonMS]

Nice one!

+1 on the E2E test if possible, though if it ends up being complicated for some reason we could proceed with out it for now.

[TanayParikh]

Did the manual validation by running the GlobalizationWasmApp test app. Will add the E2E tests when merging into main. Thanks for the reviews.

[ghost]

Hello human! Please make sure you've included the Shiproom Template in a comment or (preferably) the PR description. Also, make sure this PR is not marked as a draft and is ready-to-merge.