[kpm] Implement generic 'kotlin.debug' extra

^KT-52568 In Progress

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/kpm/idea/ideaKpmProjectModelBuilderFactory.kt

@@ -8,6 +8,7 @@
 package org.jetbrains.kotlin.gradle.kpm.idea
 
 import org.jetbrains.kotlin.gradle.kpm.external.ExternalVariantApi
+import org.jetbrains.kotlin.gradle.kpm.idea.serialize.IdeaKpmExtrasSerializer
 import org.jetbrains.kotlin.gradle.plugin.mpp.pm20.GradleKpmFragmentGranularMetadataResolverFactory
 import org.jetbrains.kotlin.gradle.plugin.mpp.pm20.KotlinPm20ProjectExtension
 import org.jetbrains.kotlin.tooling.core.UnsafeApi
@@ -95,4 +96,9 @@ internal fun IdeaKpmProjectModelBuilder.Companion.default(
         effect = IdeaKpmMissingFileDependencyLogger,
         constraint = IdeaKpmProjectModelBuilder.FragmentConstraint.unconstrained
     )
+
+    registerExtrasSerializationExtension {
+        /* For transporting debugging breadcrumbs into the ide */
+        register(kotlinDebugKey, IdeaKpmExtrasSerializer.javaIoSerializable())
+    }
 }

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/kpm/idea/kotlinDebugKey.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.gradle.kpm.idea
+
+import org.jetbrains.kotlin.tooling.core.Extras
+import org.jetbrains.kotlin.tooling.core.MutableExtras
+import org.jetbrains.kotlin.tooling.core.extrasKeyOf
+
+internal val kotlinDebugKey = extrasKeyOf<Any>("kotlin.debug")
+
+val Extras.kotlinDebug get() = this[kotlinDebugKey]
+
+var MutableExtras.kotlinDebug: Any?
+    get() = this[kotlinDebugKey]
+    set(value) {
+        if (value != null) this[kotlinDebugKey] = value
+        else this.remove(kotlinDebugKey)
+    }