Streamline uninstall

Please let me know if this is the wrong repo for this, @tailhook.

The process for uninstalling EdgeDB requires many steps:

1. `edgedb instance list`
2. `edgedb instance destroy -I ` for each instance listed
3. `edgedb server uninstall` (which, I believe, will install all server versions not in use by an instance)
4. `edgedb info`
5. Delete each directory mentioned in that output
6. Locate the CLI binary (via `which` or `Get-Command` in Windows/Powershell) and delete

I would like to see us provide users a simpler way to uninstall. Can this be done using the CLI? Could a `edgedb uninstall` command automate this process, ultimately deleting itself?