Use autolayout for loading indicator

[antrix1989]

Proposed changes

Fix webview layout in sample app on mac and update common core. Core pr: AzureAD/microsoft-authentication-library-common-for-objc#1628

Type of change

• Feature work
• Bug fix
• Documentation
• Engineering change
• Test
• Logging/Telemetry

Risk

• High – Errors could cause MAJOR regression of many scenarios. (Example: new large features or high level infrastructure changes)
• Medium – Errors could cause regression of 1 or more scenarios. (Example: somewhat complex bug fixes, small new features)
• Small – No issues are expected. (Example: Very small bug fixes, string changes, or configuration settings changes)

Additional information

[Copilot]

Pull request overview

This PR refactors the macOS test app's UI to use Auto Layout constraints for the web view instead of manual frame-based positioning. The changes improve layout flexibility and maintainability.

Key Changes

• Replaced frame-based WKWebView positioning with Auto Layout constraints
• Changed acquireTokenView from NSStackView to NSView to accommodate the new layout approach
• Updated the storyboard to restructure the view hierarchy with proper Auto Layout constraints

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
MSALAcquireTokenViewController.m	Changed webView initialization to use Auto Layout with zero frame and added pin-to-edges constraints
Base.lproj/Main.storyboard	Restructured view hierarchy, replacing NSStackView with NSView and adding constraint-based layout
IdentityCore	Updated subproject commit reference

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