Prohibit having duplicate parameter names in functional types

#KT-15804 Fixed

compiler/testData/diagnostics/tests/redeclarations/DuplicateParameterNamesInFunctionType.kt

@@ -0,0 +1,7 @@
+fun test0(f: (String, String) -> Unit) {
+    f("", "")
+}
+
+fun test1(f: (<!DUPLICATE_PARAMETER_NAME_IN_FUNCTION_TYPE!>a<!>: Int, <!DUPLICATE_PARAMETER_NAME_IN_FUNCTION_TYPE!>a<!>: Int) -> Unit) {
+    f(1, 1)
+}

compiler/testData/diagnostics/tests/redeclarations/DuplicateParameterNamesInFunctionType.txt

@@ -0,0 +1,4 @@
+package
+
+public fun test0(/*0*/ f: (kotlin.String, kotlin.String) -> kotlin.Unit): kotlin.Unit
+public fun test1(/*0*/ f: (a: kotlin.Int, a: kotlin.Int) -> kotlin.Unit): kotlin.Unit