K2: build SAM-based function type for a given captured type properly

Before this commit, we assumed (erroneously) that a captured type
cannot have an associated SAM-based function type.
In this commit we changed this assumption, replacing a captured type
with its lower type for this purpose

#KT-63379 Fixed

compiler/testData/diagnostics/tests/funInterface/unitInContravariantPosition.fir.kt

@@ -1,17 +0,0 @@
-// ISSUE: KT-63379
-
-class TestDummyClass<T> {
-    fun testFun(t: T) {}
-}
-
-fun more(t: TestDummyClass<in CustomRunnable>) {
-    t.testFun <!ARGUMENT_TYPE_MISMATCH!>{ Unit }<!>
-    t.testFun(CustomRunnable { Unit })
-    t.testFun(object : CustomRunnable {
-        override fun run() {}
-    })
-}
-
-fun interface CustomRunnable {
-    fun run()
-}

compiler/testData/diagnostics/tests/funInterface/unitInContravariantPosition.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // ISSUE: KT-63379
 
 class TestDummyClass<T> {

compiler/testData/diagnostics/tests/funInterface/unitInCovariantPosition.fir.kt

@@ -0,0 +1,17 @@
+// ISSUE: KT-63379 (modified example, see original in unitInContravariantPosition.kt)
+
+class TestDummyClass<T> {
+    fun testFun(t: T) {}
+}
+
+fun more(t: TestDummyClass<out CustomRunnable>) {
+    t.testFun <!ARGUMENT_TYPE_MISMATCH!>{ Unit }<!>
+    t.testFun(<!ARGUMENT_TYPE_MISMATCH!>CustomRunnable { Unit }<!>)
+    t.testFun(<!ARGUMENT_TYPE_MISMATCH!>object : CustomRunnable<!> {
+        override fun run() {}
+    })
+}
+
+fun interface CustomRunnable {
+    fun run()
+}

compiler/testData/diagnostics/tests/funInterface/unitInCovariantPosition.kt

@@ -0,0 +1,17 @@
+// ISSUE: KT-63379 (modified example, see original in unitInContravariantPosition.kt)
+
+class TestDummyClass<T> {
+    fun testFun(t: T) {}
+}
+
+fun more(t: TestDummyClass<out CustomRunnable>) {
+    t.testFun <!TYPE_MISMATCH!>{ Unit }<!>
+    t.testFun(<!TYPE_MISMATCH!>CustomRunnable { Unit }<!>)
+    t.testFun(<!TYPE_MISMATCH!>object : CustomRunnable<!> {
+        override fun run() {}
+    })
+}
+
+fun interface CustomRunnable {
+    fun run()
+}