Check also drop-box content in multi-module line marker tests

Related to KT-26957

idea/testData/multiModuleLineMarker/actualConstructorWithProperties/jvm/jvm.kt

@@ -1 +1,11 @@
-actual class <lineMarker>WithConstructor</lineMarker> actual constructor(actual val x: Int, actual val s: String)
+actual class <lineMarker descr="Has declaration in common module">WithConstructor</lineMarker> actual constructor(actual val x: Int, actual val s: String)
+
+/*
+LINEMARKER: Has declaration in common module
+TARGETS:
+common.kt
+expect class <1>WithConstructor(x: Int, s: String) {
+    val <3>x: Int
+
+    val <2>s: String
+*/