fix(material/button-toggle): use radio pattern for single select Mat toggle button group

[clamli]

This commit updates the single-select Mat toggle button group to use radio pattern. This way the exclusiveness of the selection can be conveyed to the screen reader users.

[github-actions[bot]]

Deployed dev-app for 119797c11ec1ab34c85394ff6ce4ff83500ac1bd to: https://ng-dev-previews-comp--pr-angular-components-28505-dev-r8qalkt6.web.app

Note: As new commits are pushed to this pull request, this link is updated after the preview is rebuilt.

[zarend]

We're considering using a different approach to make it easier to land, see #28548

[crisbeto]

Given that #28548 was merged, I'm assuming that we can close this PR.