Loosen tail-call optimization check for functions returning Unit

Do not check, that all Unit predecessors are POPs. This is safe for the
same reason, as it is safe to allow some of ARETURN sources not be
suspension point results.
To elaborate, before Unit, the stack is empty. This is because if there
are multiple paths to Unit and at least one of them comes from POP after
suspension point (we are interested in this case only - otherwise, the
call is not tail-call), in path from said POP the stack is empty, since
after suspension point the stack contains only one element. Thus, the
stack in other paths leading to Unit has to be empty, otherwise, merge
operation is not possible and ASM will report error during analysis.
Since the stack is empty in all paths, we can hoist Unit and following
ARETURN to predecessors, effectively turning path from suspension point
to tail-call.

compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -9683,6 +9683,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                     runTest("compiler/testData/codegen/box/coroutines/tailCallOptimizations/unit/functionReference.kt");
                 }
 
+                @TestMetadata("inline.kt")
+                public void testInline() throws Exception {
+                    runTest("compiler/testData/codegen/box/coroutines/tailCallOptimizations/unit/inline.kt");
+                }
+
                 @TestMetadata("override.kt")
                 public void testOverride() throws Exception {
                     runTest("compiler/testData/codegen/box/coroutines/tailCallOptimizations/unit/override.kt");