Update angular to v15 and refactor deprecated code

[benceHornyak]

What does this PR do?

Upgrades Angular, CDK and material all the way to the latest angular v15

Test Plan

Everything works just like before.

See the screenshot:

Related PRs and Issues

Closes https://github.com/appwrite/demos-for-angular/issues/16

Have you read the Contributing Guidelines on issues?

Yes.