FIR: support type inference for assignments, fix related lambda inference

compiler/fir/resolve/testData/resolve/stdlib/hashSet.kt

@@ -7,7 +7,14 @@ var b: MutableSet<String>? = null
         field = HashSet()
     }
 
+var <T> MutableSet<T>.d: T? get() = null
+    set(_) {}
+
+fun <T> produce(): T = TODO()
+
 fun foo() {
     var c: MutableSet<String>? = null
     c = HashSet()
+
+    c!!.d = produce()
 }

compiler/fir/resolve/testData/resolve/stdlib/hashSet.txt

@@ -4,9 +4,27 @@ FILE: hashSet.kt
     public final var b: R|kotlin/collections/MutableSet<kotlin/String>|? = Null(null)
         public get(): R|kotlin/collections/MutableSet<kotlin/String>|?
         public set(_: R|kotlin/collections/MutableSet<kotlin/String>|?): R|kotlin/Unit| {
-            F|/b| = R|java/util/HashSet.HashSet|()
+            F|/b| = R|java/util/HashSet.HashSet|<R|kotlin/String|>()
         }
+    public final var <T> R|kotlin/collections/MutableSet<T>|.d: R|T|?
+        public get(): R|T|? {
+            ^ Null(null)
+        }
+        public set(_: R|T|?): R|kotlin/Unit| {
+        }
+    public final fun <T> produce(): R|T| {
+        ^produce R|kotlin/TODO|()
+    }
     public final fun foo(): R|kotlin/Unit| {
         lvar c: R|kotlin/collections/MutableSet<kotlin/String>|? = Null(null)
-        R|<local>/c| = R|java/util/HashSet.HashSet|()
+        R|<local>/c| = R|java/util/HashSet.HashSet|<R|kotlin/String|>()
+        when (lval <bangbang>: R|kotlin/collections/MutableSet<kotlin/String>|? = R|<local>/c|) {
+            ==($subj$, Null(null)) ->  {
+                throw R|kotlin/KotlinNullPointerException.KotlinNullPointerException|()
+            }
+            else ->  {
+                R|<local>/<bangbang>|!
+            }
+        }
+        .R|/d| = R|/produce|<R|T|?>()
     }