Custom AWS Lambda Base Images for Java 17 and 18

After a year, Amazon still hasn't released an officially-supported AWS Lambda Base Image or Runtime for Java 17. But I needed it, so I made one. You can find the images themselves at https://gallery.ecr.aws/aleph0io/lambda/java, and the source code on GitHub at https://github.com/aleph0io/aws-lambda-java-base-images.