[Gradle][MPP] Fix KotlinProjectStructureMetadataSerializationTest.sampleMetadata

This object did not list 'commonMain' and put non-idiomatic
data into 'sourceSetNamesByVariantName'

^KT-48135 Verification Pending

libraries/tools/kotlin-gradle-plugin/src/functionalTest/kotlin/org/jetbrains/kotlin/gradle/KotlinProjectStructureMetadataSerializationTest.kt

@@ -20,15 +20,18 @@ class KotlinProjectStructureMetadataSerializationTest {
 
     private val sampleMetadata = KotlinProjectStructureMetadata(
         sourceSetNamesByVariantName = mapOf(
-            "sourceSetA" to setOf("value1", "value2"), "sourceSetB" to setOf("value3", "value4"), "sourceSetC" to setOf("value5")
+            "variant1" to setOf("commonMain", "sourceSetA", "sourceSetB"),
+            "variant2" to setOf("commonMain", "sourceSetC")
         ),
         sourceSetsDependsOnRelation = mapOf(
+            "commonMain" to emptySet(),
             "sourceSetA" to setOf("commonMain"),
             "sourceSetB" to setOf("commonMain", "sourceSetA"),
             "sourceSetC" to setOf("commonMain", "sourceSetB")
         ),
         sourceSetBinaryLayout = mapOf("sourceSetA" to METADATA, "sourceSetB" to KLIB, "sourceSetC" to KLIB),
         sourceSetModuleDependencies = mapOf(
+            "commonMain" to emptySet(),
             "sourceSetA" to setOf(ModuleDependencyIdentifier("aa", "bb")),
             "sourceSetB" to setOf(ModuleDependencyIdentifier("cc", "dd"), ModuleDependencyIdentifier("ee", "ff")),
             "sourceSetC" to emptySet()
@@ -36,7 +39,7 @@ class KotlinProjectStructureMetadataSerializationTest {
         sourceSetCInteropMetadataDirectory = mapOf("sourceSetB" to "xx/cinterop/", "sourceSetC" to "cinterops/C"),
         hostSpecificSourceSets = setOf("sourceSetC"),
         isPublishedAsRoot = true,
-        sourceSetNames = setOf("sourceSetA", "sourceSetB", "sourceSetC"),
+        sourceSetNames = setOf("commonMain", "sourceSetA", "sourceSetB", "sourceSetC"),
     )
 
     @Test