config(amazonq): codewhisperer endpoint via settings.json (aws#7761)

## Problem


## Solution
allow devs to configure Q endpoint via vscode settings.json
```
"aws.dev.codewhispererService": {
        "endpoint": "https://codewhisperer/endpoint/",
        "region": "us-east-1"
    }
```


---

- 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: Will-ShaoHua

packages/amazonq/src/lsp/client.ts

@@ -39,6 +39,7 @@ import {
     getClientId,
     extensionVersion,
     isSageMaker,
+    DevSettings,
 } from 'aws-core-vscode/shared'
 import { processUtils } from 'aws-core-vscode/shared'
 import { activate } from './chat/activation'
@@ -129,6 +130,15 @@ export async function startLanguageServer(
 
     await validateNodeExe(executable, resourcePaths.lsp, argv, logger)
 
+    const endpointOverride = DevSettings.instance.get('codewhispererService', {}).endpoint ?? undefined
+    const textDocSection = {
+        inlineEditSupport: Experiments.instance.get('amazonqLSPNEP', true),
+    } as any
+
+    if (endpointOverride) {
+        textDocSection.endpointOverride = endpointOverride
+    }
+
     // Options to control the language client
     const clientOptions: LanguageClientOptions = {
         // Register the server for json documents
@@ -177,9 +187,7 @@ export async function startLanguageServer(
                         showLogs: true,
                     },
                     textDocument: {
-                        inlineCompletionWithReferences: {
-                            inlineEditSupport: Experiments.instance.get('amazonqLSPNEP', true),
-                        },
+                        inlineCompletionWithReferences: textDocSection,
                     },
                 },
                 contextConfiguration: {