[uast visitor] optimization: convert to uast only while in qualified reference

otherwise we might have converted the whole file in the hope to find import statement

GitOrigin-RevId: e1d8d94b190e720509723ac8c082f0cc997c112a

jvm/jvm-analysis-java-tests/testSrc/com/intellij/codeInspection/tests/java/JavaJavaApiUsageInspectionTest.kt

@@ -66,6 +66,7 @@ class JavaJavaApiUsageInspectionTest : JavaApiUsageInspectionTestBase() {
   fun `test annotation`() {
     myFixture.setLanguageLevel(LanguageLevel.JDK_1_6)
     myFixture.testHighlighting(JvmLanguage.JAVA, """
+      import java.lang.SafeVarargs;
       class Annotation {
         @<error descr="Usage of API documented as @since 1.7+">SafeVarargs</error>
         public final void a(java.util.List<String>... ls) {}