[FIR] Replace lists with Long in Modifier, refactor Modifier and derived classes

compiler/fir/analysis-tests/testData/resolve/diagnostics/incompatibleModifiers.fir.txt

@@ -1,10 +1,4 @@
 FILE: incompatibleModifiers.kt
-    public final class A<out T> : R|kotlin/Any| {
-        public constructor<out T>(): R|A<T>| {
-            super<R|kotlin/Any|>()
-        }
-
-    }
     private final class B : R|kotlin/Any| {
         public constructor(): R|B| {
             super<R|kotlin/Any|>()

compiler/fir/analysis-tests/testData/resolve/diagnostics/incompatibleModifiers.kt

@@ -1,5 +1,3 @@
-class A<<!INCOMPATIBLE_MODIFIERS!>in<!> <!INCOMPATIBLE_MODIFIERS!>out<!> T> {  }
-
 <!INCOMPATIBLE_MODIFIERS!>private<!> <!INCOMPATIBLE_MODIFIERS!>public<!> class B
 <!INCOMPATIBLE_MODIFIERS!>protected<!> <!INCOMPATIBLE_MODIFIERS!>internal<!> class C