Login with Az module with read only permissions for one session only

## Description of the new feature
I often find myself browsing around in customer tenants in order to either solve problems or doing assessments. I often use my CSP admin for this, much better than creating a dedicated user per tenant I work in. It has happened before that I've modified or deleted resources by mistake.

With a "read only" option for current session, you'd have one more safety barrier to keep you from human mistakes.

## Proposed implementation details (optional)
It would be awesome if you could add a switch to the "Connect-AzAccount" cmdlet to only enable read only cmdlets during the session. If I we're to pass a "Set-Az*" or smililar, the module would return a error saying that read only is enabled for current session.

This could be solved at PowerShell module level (I imagine), or you'd have to use AZ together with Azure to create a temporary identity with limited permissions or similar.