[FIR] Implement INCORRECT_CHARACTER_LITERAL, EMPTY_CHARACTER_LITERAL, TOO_MANY_CHARACTERS_IN_CHARACTER_LITERAL, ILLEGAL_ESCAPE, ILLEGAL_ESCAPE_SEQUENCE diagnostics, fix tests

compiler/fir/tree/src/org/jetbrains/kotlin/fir/diagnostics/ConeSimpleDiagnostic.kt

@@ -30,5 +30,11 @@ enum class DiagnosticKind {
     UnknownCallableKind,
     IllegalProjectionUsage,
     MissingStdlibClass,
+
+    IncorrectCharacterLiteral,
+    EmptyCharacterLiteral,
+    TooManyCharactersInCharacterLiteral,
+    IllegalEscape,
+
     Other
 }