KT-50728 Enforce receiver type resolve

When stdlib is represented as a source dependency (which seems to be the
case in the `kotlin` project), it will be resolved lazily for the IDE.
Same thing can happen if someone decides to "extend" the stdlib
by declaring their declaration in the `kotlin` package

In both of those cases, we need to make sure that receiver type is fully
resolved before trying to get a `coneType` from it

N.B. To make resolve tests work, I've added a separate folder
`withAllowedKotlinPackage` to the `testData`, because in the default
test setup it is not allowed to extend the `kotlin` package by user's
definitions

^KT-50728 Fixed

compiler/fir/analysis-tests/testData/resolve/withAllowedKotlinPackage/extensionFunctionAddedToStdlib.fir.txt

@@ -0,0 +1,24 @@
+FILE: main.kt
+    package test
+
+    public final class TestClass : R|kotlin/Any| {
+        public constructor(): R|test/TestClass| {
+            super<R|kotlin/Any|>()
+        }
+
+        public final fun test(): R|kotlin/Unit| {
+            <Unresolved name: extensionFun>#()
+        }
+
+    }
+FILE: stdlibExt.kt
+    package kotlin
+
+    public final class MyClass : R|kotlin/Any| {
+        public constructor(): R|kotlin/MyClass| {
+            super<R|kotlin/Any|>()
+        }
+
+    }
+    public final fun R|kotlin/MyClass|.extensionFun(): R|kotlin/Unit| {
+    }

compiler/fir/analysis-tests/testData/resolve/withAllowedKotlinPackage/extensionFunctionAddedToStdlib.kt

@@ -0,0 +1,15 @@
+// FILE: main.kt
+package test
+
+class TestClass {
+    fun test() {
+        <!UNRESOLVED_REFERENCE!>extensionFun<!>()
+    }
+}
+
+// FILE: stdlibExt.kt
+package kotlin
+
+class MyClass
+
+fun MyClass.extensionFun() {}