Support additional flags in MPP tests. Add diagnostic tests for defaults

idea/testData/multiplatform/jvmDefaultNonMpp/base/base.kt

@@ -0,0 +1,9 @@
+package base
+
+interface Check {
+    fun test(): String {
+        return "fail";
+    }
+}
+
+open class CheckClass : Check

idea/testData/multiplatform/jvmDefaultNonMpp/clash/clash.kt

@@ -0,0 +1,9 @@
+import base.*
+
+interface SubCheck : Check {
+    override fun test(): String {
+        return "OK"
+    }
+}
+
+class <!EXPLICIT_OVERRIDE_REQUIRED_IN_MIXED_MODE("public open fun test(): String defined in SubCheckClass", "public open fun test(): String defined in base.CheckClass", "all-compatibility")!>SubCheckClass<!> : CheckClass(), SubCheck

idea/testData/multiplatform/jvmDefaultNonMpp/dependencies.txt

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+MODULE base { platform=[JVM]; root=base;  additionalCompilerArgs=-Xjvm-default=disable }
+MODULE clash { platform=[JVM]; root=clash; additionalCompilerArgs=-Xjvm-default=all-compatibility }
+
+clash -> base { kind=DEPENDS_ON }