Upgrade the build to Java 25

[sdeleuze]

Spring Framework build currently uses Java 24 (with -release 17 to retain the Java 17 baseline), it should be upgraded to Java 25 which will have long terms support for most vendors, like Liberica JDK that Spring is using. Another reason is that Java 25 is the recommended version with our next major.

Draft branch with MultipartWebClientIntegrationTests broken is available at https://github.com/sdeleuze/spring-framework/tree/java25.