*.gradle.kts: include project sources in script dependencies sources scope

^KT-39523 Fixed

idea/testData/script/definition/navigation/buildSrcProblem/depModule/test/custom.kt

@@ -0,0 +1,7 @@
+package test
+
+object KObject {
+    fun foo() {
+
+    }
+}

idea/testData/script/definition/navigation/buildSrcProblem/script.kts

@@ -0,0 +1,6 @@
+test.KObject.<caret>foo()
+
+// DEPENDENCIES: classpath:module-classes; sources:module-source
+
+// REF: (in test.KObject).foo()
+// FILE: test/custom.kt