FIR IDE: Search for the first non-local declaration in EnclosingDeclarationContext::detect

Local declarations do not have a stable `ClassId`, which is used in
`declarationUtils.collectDesignation`. Local classes will always have
`outerClassId.isLocal = true`, even when it is not true (see
`org.jetbrains.kotlin.fir.builder.Context.currentClassId` for why this
happens)

idea/idea-completion/testData/basic/common/primitiveCompletion/localClassConstructor.kt

@@ -0,0 +1,20 @@
+package test
+
+class T
+
+fun topLevelFun(param: T) {
+    val firstVariable = T()
+
+    class LocalClass(constructorParam: T) {
+        val localClassField = constructorParam
+
+        init {
+            <caret>
+        }
+    }
+
+    val secondVariable = T()
+}
+
+// EXIST: firstVariable, param, constructorParam, localClassField
+// ABSENT: secondVariable