Close #784 and update contribution guides, etc. to push users to file separate issues for each type problem

[alex-frankel]

Goal is to stop the bleeding with the #784 megathread with the long term goal of triaging that thread and filing separate issues in the bicep az types repo.

[majastrz]

We need to update the link from the aka.ms bicep types issue link and will also need to create an issue template or form in the bicep-types-az repo.