K2 Scripting tests: adding tests on script decls visibility

fixes (makes it stable) behavior of the script top-level declarations
visibility in K2 scripts

compiler/fir/analysis-tests/testData/resolve/scripts/scriptsDeclsMayConflict.kts

@@ -0,0 +1,12 @@
+
+// FILE: script1.kts
+
+val a = 42
+
+// FILE: script2.kts
+
+val a = "42"
+
+// FILE: main.kt
+
+fun foo() =  <!OVERLOAD_RESOLUTION_AMBIGUITY!>a<!>