Migrate boxInline tests to new multi-file framework

compiler/testData/codegen/boxInline/simple/severalUsage.kt

@@ -0,0 +1,21 @@
+// FILE: 1.kt
+
+public inline fun <R> runTest(f: () -> R): R {
+    return f()
+}
+
+public inline fun <R> minByTest(f: (Int) -> R): R {
+    var minValue = f(1)
+    val v = f(1)
+    return v
+}
+
+// FILE: 2.kt
+
+fun box(): String {
+    val result = runTest{minByTest<Int> { it }}
+
+    if (result != 1) return "test1: ${result}"
+
+    return "OK"
+}