IR: make calls with explicit singleton receiver tailrec [KT-48602]

compiler/testData/diagnostics/tests/tailRecSingleton.fir.kt

@@ -7,8 +7,8 @@ object Foo {
         this.foo2()
     }
 
-    <!NO_TAIL_CALLS_FOUND!>tailrec fun foo3()<!> {
-        Foo.<!NON_TAIL_RECURSIVE_CALL!>foo3<!>()
+    tailrec fun foo3() {
+        Foo.foo3()
     }
 }
 
@@ -22,12 +22,12 @@ class Bar {
             this.bar2()
         }
 
-        <!NO_TAIL_CALLS_FOUND!>tailrec fun bar3()<!> {
-            Bar.<!NON_TAIL_RECURSIVE_CALL!>bar3<!>()
+        tailrec fun bar3() {
+            Bar.bar3()
         }
 
-        <!NO_TAIL_CALLS_FOUND!>tailrec fun bar4()<!> {
-            Bar.Companion.<!NON_TAIL_RECURSIVE_CALL!>bar4<!>()
+        tailrec fun bar4() {
+            Bar.Companion.bar4()
         }
     }
 }

compiler/testData/diagnostics/tests/tailRecursionComplex.fir.kt

@@ -1,16 +0,0 @@
-object O {
-    // foo is the same, but the compiler currently doesn't compile this as tail recursive. See KT-48602
-    <!NO_TAIL_CALLS_FOUND!>tailrec fun foo(i: Int): Int<!> = if (i < 0) 0 else O.<!NON_TAIL_RECURSIVE_CALL!>foo<!>(i - 1)
-}
-
-class A {
-    <!NO_TAIL_CALLS_FOUND!>tailrec fun foo(i: Int)<!> = if (i < 0) 0 else A.foo(i - 1)
-
-    companion object {
-        fun foo(i: Int) = 42 + i
-    }
-}
-
-class B {
-    <!NO_TAIL_CALLS_FOUND!>tailrec fun foo(i: Int)<!> = if (i < 0) 0 else O.foo(i - 1)
-}

compiler/testData/diagnostics/tests/tailRecursionComplex.kt

@@ -1,5 +1,6 @@
+// FIR_IDENTICAL
 object O {
-    // foo is the same, but the compiler currently doesn't compile this as tail recursive. See KT-48602
+    // tailrec since `O` is a singleton
     tailrec fun foo(i: Int): Int = if (i < 0) 0 else O.foo(i - 1)
 }