Switch to use ZIO Schema for derivation

[jdegoes]

Rather than use Magnolia or custom macros, we can switch to ZIO Schema, which will soon feature derivation for Scala 2.x and Scala 3.x, which also supports annotations.

Once we have ZIO schema, we can provide some helper methods which do not require or refer to ConfigDescriptor, e.g.:

def loadConfig[A](implicit schema: Schema[A]): ZIO[Has[ConfigSource], Throwable, A] = ???

[afsalthaj]

Is this going to replace zio-config-magnolia or add as another module (and in future deprecate zio-config-magnolia) ?