[FIR] Support 4 diagnostics for pairs of modifiers

In particular, this commit includes:
* Attempt to abstract access to FirSourceElement via FirModifier
* Add more visit functions to DeclarationCheckersDiagnosticComponent
* Add messages+factories for 4 modifier-related errors and warnings
* Introduce FirModifierChecker

compiler/testData/diagnostics/tests/dataClasses/dataInheritance.fir.kt

@@ -2,7 +2,7 @@ interface SuperInterface
 
 open class SuperClass
 
-abstract data class Base(val x: Int)
+<!INCOMPATIBLE_MODIFIERS!>abstract<!> <!INCOMPATIBLE_MODIFIERS!>data<!> class Base(val x: Int)
 
 class Derived: Base(42)
 

compiler/testData/diagnostics/tests/dataClasses/innerDataClass.fir.kt

@@ -1,3 +0,0 @@
-class Outer {
-    inner data class Inner(val x: Int)
-}

compiler/testData/diagnostics/tests/dataClasses/innerDataClass.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class Outer {
     <!INCOMPATIBLE_MODIFIERS!>inner<!> <!INCOMPATIBLE_MODIFIERS!>data<!> class Inner(val x: Int)
 }

compiler/testData/diagnostics/tests/dataClasses/innerOuterDataClass.fir.kt

@@ -1 +1 @@
-inner data class Outer(val x: Int)
+<!INCOMPATIBLE_MODIFIERS!>inner<!> <!INCOMPATIBLE_MODIFIERS!>data<!> class Outer(val x: Int)

compiler/testData/diagnostics/tests/dataClasses/sealedDataClass.fir.kt

@@ -1,4 +0,0 @@
-sealed data class My(val x: Int) {
-    object Your: My(1)
-    class His(y: Int): My(y)
-}

compiler/testData/diagnostics/tests/dataClasses/sealedDataClass.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 <!INCOMPATIBLE_MODIFIERS!>sealed<!> <!INCOMPATIBLE_MODIFIERS!>data<!> class My(val x: Int) {
     object Your: My(1)
     class His(y: Int): My(y)