Add required permissions to each cmdlet

With the recent changes to the app registration for the module, it would be great to have a consistent bit of info on each cmdlet showing which permissions are required for it to work. Some cmdlets have this already, like Get-PnPAzureADAppSitePermission. Others, like Get-PnPSite do not.

If there's a way to generate a list of cmdlets which don't have this info, we could crowdsource the content.

Understanding what permissions are required to accomplish specific things can be problematic, as shown in issue #4351. While it might seem anyone running PnP.PowerShell should inherently know which permissions are required, I'm positive that's not the case. It certainly isn't obvious to me most of the time, now that I'm having to think about it with the recent changes. In many cases, we have to ask someone else to consent to the permissions (totally reasonable) and it is important we know which permissions to ask for.

Start by comparing the permission information on Get-PnPAzureADAppSitePermission with the missing information on Get-PnPSite, then review issue #4351 for the permission context. Identify the cmdlets lacking this information and document the required permissions consistently for each; a complete list and consistent cmdlet documentation mark the work done.