[FIR] Report empty intersection on responsible call

When reporting INFERRED_TYPE_VARIABLE_INTO_EMPTY_INTERSECTION, search
for a call to a declaration with the type parameter that got inferred
into an empty intersection inside the expression.

#KT-56377 Fixed

compiler/testData/diagnostics/tests/inference/coercionToUnit/afterBareReturn.fir.kt

@@ -0,0 +1,41 @@
+interface I
+open class C
+
+fun completed(): String = "..."
+
+fun <T> incomplete(): T = null!!
+
+fun <T : I> incompatibleI(): T = null!!
+fun <T : C> incompatibleC(): T = null!!
+
+val p = false
+
+fun expectUnit(x: Unit) = x
+
+fun test1() = run {
+    if (p) return@run
+    completed() // ok, not returned
+}
+
+fun test2() = run {
+    if (p) return@run
+    incomplete() // ? either uninferred T or Unit
+}
+
+fun test3() = run {
+    if (p) return@run
+    <!INFERRED_TYPE_VARIABLE_INTO_POSSIBLE_EMPTY_INTERSECTION!>incompatibleI<!>() // ? either uninferred T or error (Unit </: I)
+}
+
+fun test4() = run {
+    if (p) return@run
+    <!INFERRED_TYPE_VARIABLE_INTO_EMPTY_INTERSECTION_WARNING!>incompatibleC<!>() // ? either uninferred T or error (Unit </: C)
+}
+
+fun main() {
+    // all ok
+    expectUnit(test1())
+    expectUnit(test2())
+    expectUnit(test3())
+    expectUnit(test4())
+}

compiler/testData/diagnostics/tests/inference/coercionToUnit/afterBareReturn.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 interface I
 open class C