fix(toolkit): handle isCn when region is not initialized to fix extension activation failure (aws#7599)

## Problem
With updating Toolkit version to latest in SMUS CodeEditor Spaces,
observing Toolkit throws an error as attached in screenshot below with
error message
```
Attempted to get compute region without initializing
```
<img width="2039" alt="image"
src="https://github.com/user-attachments/assets/a53e8fdc-bf7b-4c96-98fa-78c6db819a72"
/>

## Solution
- Issue is due to getComputeRegion() invoked first before compute region
is initialized
- hence solution is to Make `isCn()` resilient to uninitialized state
and return a default value
- Tested with a local debug artifact in SMUS CodeEditor space, toolkit
activation completed and working
- 
<img width="1886" alt="image"
src="https://github.com/user-attachments/assets/988c208c-3fe8-4530-a477-3e8704f1f598"
/>

- Also Tested the changes in standalone VS code application and SMAI
compute instance, and toolkit explorer view is seen working as expected
- 

![image](https://github.com/user-attachments/assets/c8562928-95f9-49e3-bd0a-f1e5dfd92969)
- 

![image](https://github.com/user-attachments/assets/329f7bed-461c-4833-ba46-7b2fdc068793)
- Also tested the vsix in china region cn-north-1, and working as
expected
- 
<img width="720" height="393" alt="image"
src="https://github.com/user-attachments/assets/b0523567-82ad-4dcb-b218-a935983c3b47"
/>



---

- 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: parameja1

packages/core/src/shared/extensionUtilities.ts

@@ -194,7 +194,17 @@ export function isSageMaker(appName: 'SMAI' | 'SMUS' = 'SMAI'): boolean {
 }
 
 export function isCn(): boolean {
-    return getComputeRegion()?.startsWith('cn') ?? false
+    try {
+        const region = getComputeRegion()
+        if (!region || region === 'notInitialized') {
+            getLogger().debug('isCn called before compute region initialized, defaulting to false')
+            return false
+        }
+        return region.startsWith('cn')
+    } catch (err) {
+        getLogger().error(`Error in isCn method: ${err}`)
+        return false
+    }
 }
 
 /**

packages/core/src/test/shared/extensionUtilities.test.ts

@@ -9,7 +9,7 @@ import { AWSError } from 'aws-sdk'
 import * as sinon from 'sinon'
 import { DefaultEc2MetadataClient } from '../../shared/clients/ec2MetadataClient'
 import * as vscode from 'vscode'
-import { UserActivity, getComputeRegion, initializeComputeRegion } from '../../shared/extensionUtilities'
+import { UserActivity, getComputeRegion, initializeComputeRegion, isCn } from '../../shared/extensionUtilities'
 import { isDifferentVersion, setMostRecentVersion } from '../../shared/extensionUtilities'
 import { InstanceIdentity } from '../../shared/clients/ec2MetadataClient'
 import { extensionVersion } from '../../shared/vscode/env'
@@ -135,6 +135,73 @@ describe('initializeComputeRegion, getComputeRegion', async function () {
     })
 })
 
+describe('isCn', function () {
+    let sandbox: sinon.SinonSandbox
+    const metadataService = new DefaultEc2MetadataClient()
+
+    beforeEach(function () {
+        sandbox = sinon.createSandbox()
+    })
+
+    afterEach(function () {
+        sandbox.restore()
+    })
+
+    it('returns false when compute region is not defined', async function () {
+        // Reset the compute region to undefined first
+        const utils = require('../../shared/extensionUtilities')
+        Object.defineProperty(utils, 'computeRegion', {
+            value: undefined,
+            configurable: true,
+        })
+
+        const result = isCn()
+
+        assert.strictEqual(result, false, 'isCn() should return false when compute region is undefined')
+    })
+
+    it('returns false when compute region is not initialized', async function () {
+        // Set the compute region to "notInitialized"
+        const utils = require('../../shared/extensionUtilities')
+        Object.defineProperty(utils, 'computeRegion', {
+            value: 'notInitialized',
+            configurable: true,
+        })
+
+        const result = isCn()
+
+        assert.strictEqual(result, false, 'isCn() should return false when compute region is notInitialized')
+    })
+
+    it('returns true for CN regions', async function () {
+        sandbox.stub(metadataService, 'getInstanceIdentity').resolves({ region: 'cn-north-1' })
+        await initializeComputeRegion(metadataService, false, true)
+
+        const result = isCn()
+
+        assert.strictEqual(result, true, 'isCn() should return true for China regions')
+    })
+
+    it('returns false for non-CN regions', async function () {
+        sandbox.stub(metadataService, 'getInstanceIdentity').resolves({ region: 'us-east-1' })
+        await initializeComputeRegion(metadataService, false, true)
+
+        const result = isCn()
+
+        assert.strictEqual(result, false, 'isCn() should return false for non-China regions')
+    })
+
+    it('returns false when an error occurs', async function () {
+        const utils = require('../../shared/extensionUtilities')
+
+        sandbox.stub(utils, 'getComputeRegion').throws(new Error('Test error'))
+
+        const result = isCn()
+
+        assert.strictEqual(result, false, 'isCn() should return false when an error occurs')
+    })
+})
+
 describe('UserActivity', function () {
     let count: number
     let sandbox: sinon.SinonSandbox