[release/8.0-preview5] [Blazor] Fix WebView JavaScript boot bug (#48594)

# [Blazor] Fix WebView JavaScript boot bug

Fixes an issue where the WebView IPC receiver starts before the JavaScript dispatcher object gets initialized, preventing all Blazor Hybrid apps from starting.

## Description

Due to some recent major changes in this area, a WebView-specific initialization order bug was introduced that prevents Blazor Hybrid apps from booting correctly.

Unblocks https://github.com/dotnet/maui/pull/15415

## Customer Impact

Very large. All Blazor Hybrid apps will fail to start without a workaround.

## Regression?

- [X] Yes
- [ ] No

Regressed from .NET 8.0 Preview 4

## Risk

- [ ] High
- [ ] Medium
- [X] Low

The fix is very isolated and unlikely to introduce another bug.

## Verification

- [X] Manual (required)
- [ ] Automated

## Packaging changes reviewed?

- [ ] Yes
- [ ] No
- [X] N/A