[FIR] KT-53988: Report ILLEGAL_SELECTOR for constants as selectors

Merge-request: KT-MR-7756
Merged-by: Nikolay Lunyak <Nikolay.Lunyak@jetbrains.com>

^KT-53988 Fixed

compiler/testData/diagnostics/tests/kt53988.fir.kt

@@ -0,0 +1,6 @@
+fun main(args: Array<String>) {
+    return
+        .
+        <!ILLEGAL_SELECTOR, UNSIGNED_LITERAL_WITHOUT_DECLARATIONS_ON_CLASSPATH!>1u<!> // The expression cannot be a selector (occur after a dot)
+    throw AssertionError()
+}

compiler/testData/diagnostics/tests/kt53988.kt

@@ -0,0 +1,6 @@
+fun main(args: Array<String>) {
+    return
+        <!UNREACHABLE_CODE!>.
+        <!ILLEGAL_SELECTOR, UNSIGNED_LITERAL_WITHOUT_DECLARATIONS_ON_CLASSPATH!>1u<!><!> // The expression cannot be a selector (occur after a dot)
+    <!UNREACHABLE_CODE!>throw AssertionError()<!>
+}

compiler/testData/diagnostics/tests/kt53988.txt

@@ -0,0 +1,3 @@
+package
+
+public fun main(/*0*/ args: kotlin.Array<kotlin.String>): kotlin.Unit