Bump temurin-jdk-17 to temurin-jdk-21

[tesshucom]

Overview

Temurin's alpine-jdk17 and jammy-jdk17 will each be bumped to 21.

Details

Jpsonic provides Alpine base images and Ubunts base images. These Temurin dependencies will change with the release of Java 21.

Temurin provides a huge number of platforms, and priority has been given to the platforms with the highest priority at the time. This is the same policy this time as well, and arm-v7 is not yet available. (Or I don't know. I'm not aware of Temurin's plans for v7.) It seems that some people are using Jpsonic with v7, so it will be maintained for a while.

If this pull request is applied, the Tag and Platform Variants will be as follows.

• Java17 will of course be maintained until LTS ends. As always, binaries will also be provided.
• Java 17 used for Docker will be replaced to Java 21. Both Java 17 and Java 21 are subject to operation guarantee, but since Docker is used for speed verification, Java 21 will be targeted from now on.
• Arm v7 is not available yet, so the Jammy-Java17 combination will remain the same as before. At least...it should be usable within the Java17 LTS period.