Cleanup descriptors.proto, regenerate

- move enums and messages nested in Callable to top level, since they're likely
  to be reused in other messages soon
- delete obsolete comments: some did not any value, some became obsolete with
  custom options ("id in StringTable" -> name_id_in_table)

core/descriptor.loader.java/src/jvm_descriptors.proto

@@ -107,7 +107,7 @@ extend org.jetbrains.kotlin.serialization.Type {
   optional bool is_raw = 101;
 }
 
-extend org.jetbrains.kotlin.serialization.Callable.ValueParameter {
+extend org.jetbrains.kotlin.serialization.ValueParameter {
   // Index of the corresponding parameter of this method in JVM (counting receiver parameters, enum constructor synthetic parameters, etc.)
   optional int32 index = 100;
 }

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/kotlin/AbstractBinaryClassAnnotationAndConstantLoader.kt

@@ -138,7 +138,7 @@ public abstract class AbstractBinaryClassAnnotationAndConstantLoader<A : Any, C
             nameResolver: NameResolver,
             kind: AnnotatedCallableKind,
             parameterIndex: Int,
-            proto: ProtoBuf.Callable.ValueParameter
+            proto: ProtoBuf.ValueParameter
     ): List<A> {
         val methodSignature = getCallableSignature(callable, nameResolver, kind)
         if (methodSignature != null) {

core/descriptor.loader.java/src/org/jetbrains/kotlin/serialization/jvm/JvmProtoBuf.java

@@ -3785,14 +3785,14 @@ public final class JvmProtoBuf {
         com.google.protobuf.WireFormat.FieldType.BOOL);
   public static final int INDEX_FIELD_NUMBER = 100;
   /**
-   * <code>extend .org.jetbrains.kotlin.serialization.Callable.ValueParameter { ... }</code>
+   * <code>extend .org.jetbrains.kotlin.serialization.ValueParameter { ... }</code>
    */
   public static final
     com.google.protobuf.GeneratedMessageLite.GeneratedExtension<
-      org.jetbrains.kotlin.serialization.ProtoBuf.Callable.ValueParameter,
+      org.jetbrains.kotlin.serialization.ProtoBuf.ValueParameter,
       java.lang.Integer> index = com.google.protobuf.GeneratedMessageLite
           .newSingularGeneratedExtension(
-        org.jetbrains.kotlin.serialization.ProtoBuf.Callable.ValueParameter.getDefaultInstance(),
+        org.jetbrains.kotlin.serialization.ProtoBuf.ValueParameter.getDefaultInstance(),
         0,
         null,
         null,