Bump DDRProcessor latest_tested to 21

No issues observed in compiling manually (without the Maven
directive specifying an earlier --release) on Oracle JDK 21 GA.

cd pljava-api/src/main/java
/var/tmp/jdk-21/bin/javac -d ../../../target/classes/ \
 -Xlint:unchecked -Xlint:-removal --module-version 1.6-SNAPSHOT \
 $(find . -name '*.java')
cd ../../..
/var/tmp/jdk-21/bin/jar cf target/pljava-api-1.6-SNAPSHOT.jar \
 -C target/classes .

cd ../pljava/src/main/java
/var/tmp/jdk-21/bin/javac --module-version 1.6-SNAPSHOT \
 -d ../../../target/classes/ \
 --module-path ../../../../pljava-api/target/pljava-api-1.6-SNAPSHOT.jar \
 --processor-module-path \
  ../../../../pljava-api/target/pljava-api-1.6-SNAPSHOT.jar \
 -Xlint:unchecked -Xlint:-removal $(find . -name '*.java')
cd ../../../
/var/tmp/jdk-21/bin/jar cf target/pljava-1.6-SNAPSHOT.jar \
 -C target/classes .

cd ../pljava-examples/src/main/java
/var/tmp/jdk-21/bin/javac -d ../../../target/classes/ \
 --module-path ../../../../pljava-api/target/pljava-api-1.6-SNAPSHOT.jar \
 --processor-module-path \
  ../../../../pljava-api/target/pljava-api-1.6-SNAPSHOT.jar \
 --class-path \
  ~/.m2/repository/net/sf/saxon/Saxon-HE/10.9/Saxon-HE-10.9.jar: \
 -Xlint:unchecked -Xlint:-removal \
 --add-modules org.postgresql.pljava $(find . -name '*.java')
cd ../../../target/classes
zip -r ../pljava-examples-1.6-SNAPSHOT.jar *
# zip because jar m doesn't preserve order of manifest entries
cd ../../../
mvn clean install --projects pljava-packaging

install and test

Author: jcflack

pljava-api/src/main/java/org/postgresql/pljava/annotation/processing/DDRProcessor.java

@@ -173,7 +173,7 @@ public SourceVersion getSupportedSourceVersion()
 		 * Update latest_tested to be the latest Java release on which this
 		 * annotation processor has been tested without problems.
 		 */
-		int latest_tested = 20;
+		int latest_tested = 21;
 		int ordinal_9 = SourceVersion.RELEASE_9.ordinal();
 		int ordinal_latest = latest_tested - 9 + ordinal_9;