[FIR] Implement ASSIGNMENT_TYPE_MISMATCH, RESULT_TYPE_MISMATCH diagnostics, fix tests

compiler/testData/diagnostics/tests/subtyping/localAnonymousObjects.fir.kt

@@ -1,5 +1,5 @@
 // !DIAGNOSTICS: -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE
 fun test() {
     var x = object {}
-    x = object {}
+    x = <!ASSIGNMENT_TYPE_MISMATCH!>object<!> {}
 }

compiler/testData/diagnostics/tests/subtyping/localClasses.fir.kt

@@ -15,5 +15,5 @@ private fun foo() = run {
 
 fun test() {
     var x = foo(1)
-    x = foo()
-}
+    x = <!ASSIGNMENT_TYPE_MISMATCH!>foo()<!>
+}

compiler/testData/diagnostics/tests/subtyping/memberAnonymousObjects.fir.kt

@@ -1,6 +1,6 @@
 class Test {
     private var x = object {};
     init {
-        x = object {}
+        x = <!ASSIGNMENT_TYPE_MISMATCH!>object<!> {}
     }
 }

compiler/testData/diagnostics/tests/subtyping/nestedIntoLocalClasses.fir.kt

@@ -19,5 +19,5 @@ private fun foo() = run {
 
 fun test() {
     var x = foo(1)
-    x = foo()
-}
+    x = <!ASSIGNMENT_TYPE_MISMATCH!>foo()<!>
+}

compiler/testData/diagnostics/tests/subtyping/nestedLocalClasses.fir.kt

@@ -19,5 +19,5 @@ private fun foo() = run {
 
 fun test() {
     var x = foo(1)
-    x = foo()
-}
+    x = <!ASSIGNMENT_TYPE_MISMATCH!>foo()<!>
+}

compiler/testData/diagnostics/tests/subtyping/topLevelAnonymousObjects.fir.kt

@@ -1,5 +1,5 @@
 private var x = object {}
 
 fun test() {
-    x = object {}
-}
+    x = <!ASSIGNMENT_TYPE_MISMATCH!>object<!> {}
+}