FIR: rewrite lambda return type inference

* `return` should only be added to the last statement if the return
   type is not Unit

 * If there is a `return` without an argument, then the expected return
   type is Unit and the last expression is not a return argument (unless
   it's an incomplete call, in which case it is inferred to return Unit;
   this behavior is questionable, but inherited from K1)

 * There should be a constraint on return arguments even if the expected
   type is Unit, otherwise errors will be missed

 * When the expected type is known, using the call completion results
   writer is pointless (and probably subtly wrong).

^KT-54742 Fixed

compiler/fir/analysis-tests/testData/resolveWithStdlib/diagnostics/functionReturnTypeMismatchChecker/basic.fir.txt

@@ -48,7 +48,7 @@ FILE: basic.kt
         foo@fun <anonymous>(): R|kotlin/Unit| <inline=Unknown>  {
             ^@foo Unit
         }
-        .R|/foo|(foo@fun R|A|.<anonymous>(): R|kotlin/Unit| <inline=NoInline>  {
+        .R|/foo<Inapplicable(INAPPLICABLE): /foo>#|(foo@fun R|A|.<anonymous>(): R|kotlin/Unit| <inline=NoInline>  {
             this@R|special/anonymous|.R|/A.bar|()
             ^@foo Int(10)
         }

compiler/fir/analysis-tests/testData/resolveWithStdlib/diagnostics/functionReturnTypeMismatchChecker/basic.kt

@@ -37,7 +37,7 @@ fun errorWithLambda(): String {
         return@foo
     } foo {
         bar()
-        return@foo 10
+        return@foo <!ARGUMENT_TYPE_MISMATCH!>10<!>
     }
 
     return ""