[LL API] Add tests for 'FileBasedKotlinDeclarationProvider'

analysis/low-level-api-fir/testdata/fileBasedDeclarationProvider/simple.kt

@@ -0,0 +1,22 @@
+// CLASS: test/app/Foo
+// CLASS: test/app/Foo.Bar
+// CLASS: test/app/Foo.Bar.Baz
+// TYPE_ALIAS: test/app/MyString
+// FUNCTION: test/app/#foo
+// PROPERTY: test/app/#bar
+
+package test.app
+
+interface Foo {
+    class Bar {
+        object Baz
+    }
+
+    fun nested() {}
+}
+
+typealias MyString = String
+
+fun foo() {}
+
+val bar: String = "bar"