ArC: remove Gizmo 1 FieldDescriptors and deprecate Gizmo 1 MethodDescriptors

These classes are no longer used in ArC, because all code was migrated
to Gizmo 2 and uses `{Field,Method}Descs` instead.

Hence, `FieldDescriptors` can be removed, because it isn't `public`.
`MethodDescriptors`, on the other hand, is `public`, so we cannot
remove it immediately. Instead, we deprecate it for removal.

Note that the Gizmo 2 `{Field,Method}Descs` are both not `public`,
so they cannot be used outside ArC.

Author: Ladicek

independent-projects/arc/processor/src/main/java/io/quarkus/arc/processor/FieldDescriptors.java

@@ -50,10 +50,7 @@
 import io.quarkus.arc.impl.Sets;
 import io.quarkus.gizmo.MethodDescriptor;
 
-/**
- *
- * @author Martin Kouba
- */
+@Deprecated(forRemoval = true, since = "3.30")
 public final class MethodDescriptors {
 
     public static final MethodDescriptor FIXED_VALUE_SUPPLIER_CONSTRUCTOR = MethodDescriptor.ofConstructor(