[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 dotnet/maui#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

Author: MackinnonBuck

src/Components/Web.JS/dist/Release/blazor.webview.js

@@ -20,16 +20,16 @@ async function boot(): Promise<void> {
   }
   started = true;
 
-  const jsInitializer = await fetchAndInvokeInitializers();
-
-  startIpcReceiver();
-
   dispatcher = DotNet.attachDispatcher({
     beginInvokeDotNetFromJS: sendBeginInvokeDotNetFromJS,
     endInvokeJSFromDotNet: sendEndInvokeJSFromDotNet,
     sendByteArray: sendByteArray,
   });
 
+  const jsInitializer = await fetchAndInvokeInitializers();
+
+  startIpcReceiver();
+
   Blazor._internal.receiveWebViewDotNetDataStream = receiveWebViewDotNetDataStream;
 
   navigationManagerFunctions.enableNavigationInterception();

src/Components/Web.JS/src/Boot.WebView.ts

@@ -33,9 +33,9 @@ export function startIpcReceiver(): void {
       showErrorNotification();
     },
 
-    'BeginInvokeJS': dispatcher.beginInvokeJSFromDotNet,
+    'BeginInvokeJS': dispatcher.beginInvokeJSFromDotNet.bind(dispatcher),
 
-    'EndInvokeDotNet': dispatcher.endInvokeDotNetFromJS,
+    'EndInvokeDotNet': dispatcher.endInvokeDotNetFromJS.bind(dispatcher),
 
     'SendByteArrayToJS': receiveBase64ByteArray,