Add validation test for `@JvmMultifileClass` in Kotlin

[Godin]

See

• https://kotlinlang.org/docs/java-to-kotlin-interop.html#package-level-functions
• https://kotlinlang.org/api/core/kotlin-stdlib/kotlin.jvm/-jvm-multifile-class/

For

src/A.kt

@file:JvmName("Example")
@file:JvmMultifileClass

fun a() {
} // line 5

src/B.kt

@file:JvmName("Example")
@file:JvmMultifileClass

fun b() {
} // line 5

execution of

kotlin-2.1.10/bin/kotlinc -d classes src
javap -v -p classes/Example.class
javap -v -p classes/Example__AKt.class
javap -v -p classes/Example__BKt.class

produces

public final class Example
  minor version: 0
  major version: 52
  flags: (0x0031) ACC_PUBLIC, ACC_FINAL, ACC_SUPER
  this_class: #2                          // Example
  super_class: #4                         // java/lang/Object
  interfaces: 0, fields: 0, methods: 2, attributes: 1
{
  public static final void a();
    descriptor: ()V
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    Code:
      stack=0, locals=0, args_size=0
         0: invokestatic  #10                 // Method Example__AKt.a:()V
         3: return
      LineNumberTable:
        line 1: 0

  public static final void b();
    descriptor: ()V
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    Code:
      stack=0, locals=0, args_size=0
         0: invokestatic  #15                 // Method Example__BKt.b:()V
         3: return
      LineNumberTable:
        line 1: 0
}
RuntimeVisibleAnnotations:
  0: #16(#17=[I#18,I#19,I#20],#21=I#22,#23=I#24,#25=[s#7,s#12])
    kotlin.Metadata(
      mv=[2,1,0]
      k=4
      xi=48
      d1=["Example__AKt","Example__BKt"]
    )

final class Example__AKt
  minor version: 0
  major version: 52
  flags: (0x1030) ACC_FINAL, ACC_SUPER, ACC_SYNTHETIC
  this_class: #2                          // Example__AKt
  super_class: #4                         // java/lang/Object
  interfaces: 0, fields: 0, methods: 1, attributes: 2
{
  public static final void a();
    descriptor: ()V
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    Code:
      stack=0, locals=0, args_size=0
         0: return
      LineNumberTable:
        line 5: 0
}
SourceFile: "A.kt"
RuntimeVisibleAnnotations:
  0: #7(#8=[I#9,I#10,I#11],#12=I#13,#14=I#15,#16=[s#17],#18=[s#5,s#19],#20=s#21)
    kotlin.Metadata(
      mv=[2,1,0]
      k=5
      xi=48
      d1=["\u0000\u0006\n\u0000\n\u0002\u0010\u0002\u001a\u0006\u0010\u0000\u001a\u00020\u0001"]
      d2=["a",""]
      xs="Example"
    )

final class Example__BKt
  minor version: 0
  major version: 52
  flags: (0x1030) ACC_FINAL, ACC_SUPER, ACC_SYNTHETIC
  this_class: #2                          // Example__BKt
  super_class: #4                         // java/lang/Object
  interfaces: 0, fields: 0, methods: 1, attributes: 2
{
  public static final void b();
    descriptor: ()V
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    Code:
      stack=0, locals=0, args_size=0
         0: return
      LineNumberTable:
        line 5: 0
}
SourceFile: "B.kt"
RuntimeVisibleAnnotations:
  0: #7(#8=[I#9,I#10,I#11],#12=I#13,#14=I#15,#16=[s#17],#18=[s#5,s#19],#20=s#21)
    kotlin.Metadata(
      mv=[2,1,0]
      k=5
      xi=48
      d1=["\u0000\u0006\n\u0000\n\u0002\u0010\u0002\u001a\u0006\u0010\u0000\u001a\u00020\u0001"]
      d2=["b",""]
      xs="Example"
    )