FIR CFG: merge DFA + CFA edge in Simple edge

compiler/fir/analysis-tests/testData/resolve/smartcasts/controlStructures/returns.dot

@@ -477,7 +477,7 @@ digraph returns_kt {
     166 -> {167};
     167 -> {145};
     168 -> {169};
-    169 -> {170} [color=green];
+    169 -> {170};
     169 -> {172} [color=red];
     170 -> {171};
     171 -> {140};

compiler/fir/analysis-tests/testData/resolve/smartcasts/safeCalls/safeCalls.dot

@@ -142,7 +142,7 @@ digraph safeCalls_kt {
     47 -> {44};
     48 -> {50};
     49 -> {53};
-    50 -> {51} [color=green];
+    50 -> {51};
     50 -> {55} [color=red];
     51 -> {52};
     52 -> {49};