Fixes #2390. Fix tests according to the new method/setter rules (#2392)

Author: sgrekhov

LanguageFeatures/Extension-types/static_analysis_extension_types_A03_t05.dart

@@ -42,17 +42,11 @@ extension type ET2(int id) {
 }
 
 extension type ET3(int id) implements I1 {
-  void set n(int i) {}
-//         ^
-// [analyzer] unspecified
-// [cfe] unspecified
+  void set n(int i) {} // no error, the setter precludes the method
 }
 
 extension type ET4(int id) implements I2 {
-  int n() => 2;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
+  int n() => 2; // no error, the method precludes the setter
 }
 
 main() {

LanguageFeatures/Extension-types/static_analysis_extension_types_A30_t02.dart

@@ -30,10 +30,7 @@ extension type ET1(int id) {
 }
 
 extension type ET2(int id) implements I {
-  int get x => 42;
-//        ^
-// [analyzer] unspecified
-// [cfe] unspecified
+  int get x => 42; // no error, the getter precludes the setter
 }
 
 main() {

LanguageFeatures/Extension-types/superinterfaces_of_extension_type_A05_t08.dart

@@ -33,18 +33,21 @@
 /// redeclared by a getter, or vice versa.
 ///
 /// @description Checks that it is a compile-time error if an extension type
-/// declaration `DV` declares a member that conflicts with an inherited one
+/// declaration `DV` includes a member that conflicts with other ones
 /// @author [email protected]
 
 // SharedOptions=--enable-experiment=inline-class
 
-extension type V(int id) {
-  external int id2;
+extension type V1(int id) {
+  external int id2; // id2 here declares a setter with conflicts with V2.id2()
 }
 
-extension type ET(int id) implements V {
+extension type V2(int id) {
   int id2() => id;
-//    ^^^
+}
+
+extension type ET(int id) implements V1, V2 {
+//             ^^
 // [analyzer] unspecified
 // [cfe] unspecified
 }