K2: Avoid losing diagnostics for synthetic calls

Some of the changed tests may duplicate other existing diagnostics,
but that should not be reason not to report them at all.

There might be another job to be done to avoid diagnostic duplications

compiler/testData/diagnostics/tests/when/kt9929.fir.kt

@@ -1,4 +1,4 @@
-val test: Int = <!INITIALIZER_TYPE_MISMATCH!>if (true) {
+val test: Int = <!INITIALIZER_TYPE_MISMATCH, TYPE_MISMATCH, TYPE_MISMATCH!>if (true) {
     when (2) {
         1 -> 1
         else -> null

compiler/testData/diagnostics/tests/when/kt9972.fir.kt

@@ -10,19 +10,19 @@
  */
 
 fun test1(): Int {
-    val x: String = if (true) {
+    val x: String = <!TYPE_MISMATCH!>if (true) {
         when {
             true -> Any()
             else -> null
         }
-    } else ""
+    } else ""<!>
     return x.hashCode()
 }
 
 fun test2(): Int {
-    val x: String = <!INITIALIZER_TYPE_MISMATCH!>when {
+    val x: String = <!INITIALIZER_TYPE_MISMATCH, TYPE_MISMATCH, TYPE_MISMATCH!><!TYPE_MISMATCH!>when {
                         true -> Any()
                         else -> null
-                    } ?: return 0<!>
+                    }<!> ?: return 0<!>
     return x.hashCode()
 }

compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.fir.kt

@@ -29,7 +29,7 @@ val test3: (String) -> Boolean =
 
 val test4: (String) -> Boolean =
         when {
-            true -> { s1, <!CANNOT_INFER_PARAMETER_TYPE!>s2<!> -> true }
+            true -> <!ARGUMENT_TYPE_MISMATCH!>{ s1, <!CANNOT_INFER_PARAMETER_TYPE!>s2<!> -> true }<!>
             else -> null!!
         }