[FIR] Create error candidate for completion instead of simple error reference

compiler/testData/diagnostics/tests/inference/recursiveLocalFuns/selfCall.fir.kt

@@ -2,7 +2,7 @@
 fun foo() {
     fun bar1() = bar1()
 
-    fun bar2() = 1 + bar2()
+    fun bar2() = 1 <!AMBIGUITY!>+<!> bar2()
     fun bar3() = <!INAPPLICABLE_CANDIDATE!>id<!>(bar3())
 }
 

compiler/testData/diagnostics/tests/regressions/kt10843.fir.kt

@@ -3,6 +3,6 @@
 // See EA-76890 / KT-10843: NPE during analysis
 fun lambda(x : Int?) = x?.<!UNRESOLVED_REFERENCE!>let<!> <!UNRESOLVED_REFERENCE!>l<!> {
     y ->
-    if (y > 0) return@l x
+    if (y <!UNRESOLVED_REFERENCE!>><!> 0) return@l x
     y
 }!!