feat(lsp): add handler for openFileDiff notification (#7119)

## Problem
Handler is missing for openFileDiff lsp workspace command

## Solution
Add notification handler, extend the existing viewDiff implementation by
passing in the final content for the temp file

---

- Treat all work as PUBLIC. Private `feature/x` branches will not be
squash-merged at release time.
- Your code changes must meet the guidelines in
[CONTRIBUTING.md](https://github.com/aws/aws-toolkit-vscode/blob/master/CONTRIBUTING.md#guidelines).
- License: I confirm that my contribution is made under the terms of the
Apache 2.0 license.

Author: ctlai95

packages/amazonq/src/lsp/chat/messages.ts

@@ -39,6 +39,8 @@ import {
     ShowDocumentRequest,
     contextCommandsNotificationType,
     ContextCommandParams,
+    openFileDiffNotificationType,
+    OpenFileDiffParams,
     LINK_CLICK_NOTIFICATION_METHOD,
     LinkClickParams,
     INFO_LINK_CLICK_NOTIFICATION_METHOD,
@@ -50,7 +52,7 @@ import * as jose from 'jose'
 import { AmazonQChatViewProvider } from './webviewProvider'
 import { AuthUtil } from 'aws-core-vscode/codewhisperer'
 import { AmazonQPromptSettings, messages, openUrl } from 'aws-core-vscode/shared'
-import { DefaultAmazonQAppInitContext, messageDispatcher } from 'aws-core-vscode/amazonq'
+import { DefaultAmazonQAppInitContext, messageDispatcher, EditorContentController } from 'aws-core-vscode/amazonq'
 
 export function registerLanguageServerEventListener(languageClient: LanguageClient, provider: AmazonQChatViewProvider) {
     languageClient.info(
@@ -395,6 +397,23 @@ export function registerMessageListeners(
             params: params,
         })
     })
+
+    languageClient.onNotification(openFileDiffNotificationType.method, async (params: OpenFileDiffParams) => {
+        const edc = new EditorContentController()
+        const uri = params.originalFileUri
+        const doc = await vscode.workspace.openTextDocument(uri)
+        const entireDocumentSelection = new vscode.Selection(
+            new vscode.Position(0, 0),
+            new vscode.Position(doc.lineCount - 1, doc.lineAt(doc.lineCount - 1).text.length)
+        )
+        await edc.viewDiff({
+            context: {
+                activeFileContext: { filePath: params.originalFileUri },
+                focusAreaContext: { selectionInsideExtendedCodeBlock: entireDocumentSelection },
+            },
+            code: params.fileContent,
+        })
+    })
 }
 
 function isServerEvent(command: string) {

packages/core/src/amazonq/index.ts

@@ -47,6 +47,7 @@ export * as authConnection from '../auth/connection'
 export * as featureConfig from './webview/generators/featureConfig'
 export * as messageDispatcher from './webview/messages/messageDispatcher'
 import { FeatureContext } from '../shared/featureConfig'
+export { EditorContentController } from './commons/controllers/contentController'
 
 /**
  * main from createMynahUI is a purely browser dependency. Due to this