[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/testsWithStdLib/CallToMainRedeclaredInMultiFile.fir.kt

@@ -0,0 +1,8 @@
+// FILE: a.kt
+fun main(args: Array<String>) {}
+
+// FILE: b.kt
+fun main(args: Array<String>) {}
+
+// FILE: c.kt
+fun foo() { main(arrayOf("a", "b")) }