refactor: Migrate to JSpecify

Use this link to re-run the recipe: https://app.moderne.io/builder/o7lzAUcMZ?organizationId=T3BlblJld3JpdGU%3D

Co-authored-by: Moderne <team@moderne.io>

Author: jkschneider

plugin/src/main/java/org/openrewrite/gradle/isolated/DefaultProjectParser.java

@@ -37,6 +37,7 @@
 import org.gradle.invocation.DefaultGradle;
 import org.gradle.util.GradleVersion;
 import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet;
+import org.jspecify.annotations.Nullable;
 import org.openrewrite.*;
 import org.openrewrite.binary.Binary;
 import org.openrewrite.config.Environment;
@@ -54,7 +55,6 @@
 import org.openrewrite.internal.InMemoryLargeSourceSet;
 import org.openrewrite.internal.ListUtils;
 import org.openrewrite.internal.StringUtils;
-import org.openrewrite.internal.lang.Nullable;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.java.internal.JavaTypeCache;
 import org.openrewrite.java.marker.JavaProject;

plugin/src/main/java/org/openrewrite/gradle/isolated/ResultsContainer.java

@@ -15,8 +15,8 @@
  */
 package org.openrewrite.gradle.isolated;
 
+import org.jspecify.annotations.Nullable;
 import org.openrewrite.*;
-import org.openrewrite.internal.lang.Nullable;
 import org.openrewrite.marker.Marker;
 import org.openrewrite.marker.Markers;
 import org.openrewrite.marker.Markup;

plugin/src/main/java/org/openrewrite/gradle/isolated/package-info.java

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-@NonNullApi
+@NullMarked
 package org.openrewrite.gradle.isolated;
 
-import org.openrewrite.internal.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;