Drop old enum syntax. Comma / semicolon are now a syntactic part of enum entry.

Comma must present now between enum entries, semicolon between last entry & first member, constructor calls must be without colons / specifiers.
A swarm of tests fixed accordingly.

compiler/testData/diagnostics/tests/enum/AbstractInEnum.kt

@@ -2,6 +2,7 @@ package abstract
 
 
 enum class MyEnum() {
+    <!ABSTRACT_MEMBER_NOT_IMPLEMENTED!>INSTANCE<!>;
     //properties
     <!MUST_BE_INITIALIZED_OR_BE_ABSTRACT!>val a: Int<!>
     val a1: Int = 1