[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/inlineClasses/inlineClassDeclarationCheck.fir.kt

@@ -30,4 +30,4 @@ open inline class D1(val x: Int)
 abstract inline class D2(val x: Int)
 sealed inline class D3(val x: Int)
 
-inline data class D4(val x: String)
+<!INCOMPATIBLE_MODIFIERS!>inline<!> <!INCOMPATIBLE_MODIFIERS!>data<!> class D4(val x: String)