We need to update the docs bundle to point to the JDK 23 docs (we're currently pointing to JDK 21).

I will need to also download and host a zip bundle and add its checksum to gradle/verification-metadata.xml to avoid breaking our internal CI build.

As mentioned in JDK-8325873 when we updated the docs to use JDK 21, we should do this as a part of updating the boot JDK. To facilitate this, and to move more version number properties to a common place, I will create a new `jdk.docs.version` property in `build.properties` and put it near the `jfx.build.jdk.version` property.