JSpecify: rework tests – replace kotlin use sites to java ones with future j2k conversion

compiler/testData/foreignAnnotationsJava8/tests/jspecify/java/Defaults.java

@@ -0,0 +1,44 @@
+import org.jspecify.annotations.*;
+
+@DefaultNonNull
+public class Defaults {
+    public Foo defaultField = null;
+    @Nullable public Foo field = null;
+
+    public Foo everythingNotNullable(Foo x) { return null; }
+
+    public @Nullable Foo everythingNullable(@Nullable Foo x) { return null; }
+
+    public @NullnessUnspecified Foo everythingUnknown(@NullnessUnspecified Foo x) { return null; }
+
+    public @Nullable Foo mixed(Foo x) { return null; }
+
+    public Foo explicitlyNullnessUnspecified(@NullnessUnspecified Foo x) { return null; }
+}
+
+class Foo {
+    public Object foo() { return null; }
+}
+
+class Use {
+    static void main(Defaults a, Foo x) {
+        // jspecify_nullness_mismatch
+        a.everythingNotNullable(null).foo();
+        a.everythingNotNullable(x).foo();
+
+        a.everythingNullable(null).foo();
+
+        a.everythingUnknown(null).foo();
+
+        // jspecify_nullness_mismatch
+        a.mixed(null).foo();
+        a.mixed(x).foo();
+
+        a.explicitlyNullnessUnspecified(x).foo();
+        a.explicitlyNullnessUnspecified(null).foo();
+
+        a.defaultField.foo();
+
+        a.field.foo();
+    }
+}