 Refactor codebase to async/await - `m365 spo applicationcustomizer` & `m365 spo apppage`

This issue is for the refactoring of the `m365 spo applicationcustomizer` and `m365 spo apppage` commands, more specifically:
- m365 spo applicationcustomizer add
- m365 spo applicationcustomizer get
- m365 spo applicationcustomizer list
- m365 spo applicationcustomizer remove
- m365 spo applicationcustomizer 
- m365 spo apppage add
- m365 spo apppage set
