feat: Implement ToastLayout, remove ToastAlert

[ling1726]

Implements the ToastLayout component along with ToastTitle, ToastBody and ToastFooter.

This PR removes the existing ToastAlert component, because the new layout component handles all layout cases specified by design.

Title only:

With body and footer:

Addresse #26638

[fabricteam]

📊 Bundle size report

_{🤖 This report was generated against 54316f1ded96bffa3505140ec68031afd0cebdb6}

[codesandbox-ci[bot]]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 09a39ed708838a10f67898744ebd37fa0f42848c:

Sandbox	Source
@fluentui/react 8 starter	Configuration
@fluentui/react-components 9 starter	Configuration

[size-auditor[bot]]

Asset size changes

Size Auditor did not detect a change in bundle size for any component!

Baseline commit: 8b6d1d1fee189c864aa6a201888ed94f61b6dc7d (build)