FIR: Minor. Extract FirDeclarationsResolveTransformer::doTransformRegularClass

It's will be useful in the following commits

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirDeclarationsResolveTransformer.kt

@@ -323,12 +323,22 @@ open class FirDeclarationsResolveTransformer(transformer: FirBodyResolveTransfor
             return regularClass.runAllPhasesForLocalClass(transformer, components, data).compose()
         }
 
-        val notAnalyzed = regularClass.resolvePhase < transformerPhase
 
         return withTypeParametersOf(regularClass) {
+            doTransformRegularClass(regularClass, data)
+        }
+    }
+
+    private fun doTransformRegularClass(
+        regularClass: FirRegularClass,
+        data: ResolutionMode
+    ): CompositeTransformResult.Single<FirRegularClass> {
+        val notAnalyzed = regularClass.resolvePhase < transformerPhase
+
         if (notAnalyzed) {
             dataFlowAnalyzer.enterClass()
         }
+
         val oldConstructorScope = primaryConstructorParametersScope
         val oldContainingClass = containingClass
         primaryConstructorParametersScope = null
@@ -345,6 +355,7 @@ open class FirDeclarationsResolveTransformer(transformer: FirBodyResolveTransfor
             }
             transformDeclarationContent(regularClass, data).single as FirRegularClass
         }
+
         if (notAnalyzed) {
             if (!implicitTypeOnly) {
                 val controlFlowGraph = dataFlowAnalyzer.exitRegularClass(result)
@@ -353,11 +364,11 @@ open class FirDeclarationsResolveTransformer(transformer: FirBodyResolveTransfor
                 dataFlowAnalyzer.exitClass()
             }
         }
+
         containingClass = oldContainingClass
         primaryConstructorParametersScope = oldConstructorScope
-            @Suppress("UNCHECKED_CAST")
+        return (@Suppress("UNCHECKED_CAST")
-            result.compose()
+        result.compose())
-        }
     }
 
     override fun transformAnonymousObject(