FIR checker: skip error named reference if receiver is unresolved

Currently, FIR reports errors caused by previous resolution failure. For
example with unresolved `a` and `b` in code `a.b`, both `a` and `b` are
highlighted. FE1.0 only highlights `a` since it's the root cause. This
change applies this heuristics when reporting FirDiagnostics.

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/recursiveContractCustomContractFunction.fir.kt

@@ -32,7 +32,7 @@ fun case4() {
             run {
                 <!UNRESOLVED_REFERENCE!>s<!> = "hello"
             }
-            <!UNRESOLVED_REFERENCE!>s<!>.<!UNRESOLVED_REFERENCE!>length<!>
+            <!UNRESOLVED_REFERENCE!>s<!>.length
         }
     }
 }