azd init shows directory change preview and only warns on collisions

Incrementally adding azd to an existing project, even in very simple examples, has some minor friction in the experience:

There are no collisions in this operation, so the warning is for nothing, but it also doesn't tell me what's going to happen / end up in my directory after I continue.

- Show me a preview of the directory change
- When there are a lot of files (as is the case for large azd templates), no need to show all the nested files in a directory EXCEPT when there would be a collision, then show it
- Highlight the file collisions and let the user either - accept, skip, cancel
- If there are no collisions, just confirm they want to continue, giving them time to review the directory change preview first.

This is helpful generally, but comes out of bringing an existing agent project to a hosted agent using the agent extension: https://github.com/Azure/azure-dev/issues/6745

example: