fix: implement localStorage namespace isolation for multiple instances

[vhenckel]

Closes #8206

Describe your changes:

This PR implements automatic namespace isolation for localStorage operations in Open MCT to resolve LocalStorage contention issues when multiple instances run on the same host/port.

Summary of Changes:

1. Created NamespacedLocalStorage utility (src/utils/NamespacedLocalStorage.js):

   • Wraps localStorage operations with namespace prefixing
   • Ensures all localStorage keys are prefixed with instance namespace
   • Prevents conflicts between multiple Open MCT instances

2. Updated MCT class (src/MCT.js):

   • Added optional namespace parameter to constructor
   • Automatically generates unique namespace if not provided
   • Namespace persists across page reloads using sessionStorage
   • Added getNamespacedLocalStorage() method

3. Updated StoragePersistence (src/api/user/StoragePersistence.js):

   • Converted from singleton to class
   • Accepts namespacedLocalStorage in constructor
   • All localStorage operations now use namespace isolation

4. Updated UserAPI (src/api/user/UserAPI.js):

   • Initializes StoragePersistence with namespaced localStorage instance
   • Ensures user role storage is isolated per instance

5. Updated LocalStorageObjectProvider (src/plugins/localStorage/LocalStorageObjectProvider.js):

   • Accepts optional namespacedLocalStorage parameter
   • Maintains backward compatibility (falls back to window.localStorage if not provided)

6. Updated LocalStorage plugin (src/plugins/localStorage/plugin.js):

   • Automatically uses instance's namespaced localStorage
   • Ensures all persisted objects use namespace isolation

Key Features:

• Automatic: Namespace is generated automatically for each instance
• Persistent: Namespace persists across page reloads (same tab/window)
• Isolated: Each browser tab/window gets its own namespace
• Backward Compatible: Existing code continues to work without changes
• Transparent: All localStorage operations are automatically namespaced

How It Works:

• When an MCT instance is created, it automatically generates a unique namespace (e.g., mct-1768601842155-123456)
• This namespace is persisted in sessionStorage for the same tab
• All localStorage operations are prefixed with this namespace
• Multiple tabs/windows each get their own namespace, preventing conflicts

Testing:

• Created and tested multiple instances in separate browser tabs
• Verified localStorage isolation (objects in one tab don't appear in another)
• Verified persistence across page reloads (F5)
• Verified backward compatibility with existing code

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Is this a notable change that will require a special callout in the release notes? For example, will this break compatibility with existing APIs or projects that consume these plugins?

Author Checklist

• Changes address original issue?
• Tests included and/or updated with changes?
• Has this been smoke tested?
• Have you associated this PR with a type: label? Note: this is not necessarily the same as the original issue.
• Have you associated a milestone with this PR? Note: leave blank if unsure.
• Testing instructions included in associated issue OR is this a dependency/testcase change?

[vhenckel]

@akhenry