ImportOptimizer: add cases for unresolved references

Part of #KT-31331

nj2k/testData/newJ2k/importStatement/importWithKeywords.java

@@ -2,5 +2,8 @@
 package test;
 
 import as.type.val.var.fun.is.in.object.when.typeof;
+import as.type.val.var.fun.is.in.object.when.typeof.as;
 
-class Test {}
+class Test {
+    public void foo(as a) { }
+}

nj2k/testData/newJ2k/importStatement/importWithKeywords.kt

@@ -1,6 +1,9 @@
 // ERROR: Unresolved reference: `as`
+// ERROR: Unresolved reference: `as`
 package test
 
-import `as`.type.`val`.`var`.`fun`.`is`.`in`.`object`.`when`.`typeof`
+import `as`.type.`val`.`var`.`fun`.`is`.`in`.`object`.`when`.`typeof`.`as`
 
-internal class Test
+internal class Test {
+    fun foo(a: `as`?) {}
+}