Azure App Configuration component: use Go durations instead of nanoseconds for metadata options

[ItalyPaleAle]

The Azure App Configuration component has 4 metadata options that are durations, and those are defined as integers indicating nanoseconds (1 second =1_000_000_000 nanoseconds). This is a sub-par experience for end users.

The component should be updated to use time.Duration for those fields. The metadata parser automatically parses that as Go durations (e.g. "5s", or "2m"), which is a much better experience for users, and more aligned with the rest of Dapr.

This is a backwards-incompatible change that can be done to this alpha component.

[msfussell]

Need to also make sure this is updated dapr/docs#3595