Request to set Java 21 as minimal version

[JohnNiang]

Your current Halo version

2.20.2

Describe this feature

Although we supports Halo to run in JRE 21, we also compile Halo with JDK 17 instead of JDK 21. If we introduce dependencies which require minimal Java version of 21, Halo cannot be compiled in JDK 17. You can see the errors below when I upgrade to Lucene 10.0.0(Java 21 required):

❯ java -version
openjdk version "17.0.11" 2024-04-16 LTS
OpenJDK Runtime Environment Zulu17.50+19-CA (build 17.0.11+9-LTS)
OpenJDK 64-Bit Server VM Zulu17.50+19-CA (build 17.0.11+9-LTS, mixed mode, sharing)
❯ ./gradlew :application:compileJava

> Task :application:compileJava FAILED
/Users/johnniang/workspaces/halo-dev/halo/application/src/main/java/run/halo/app/search/lucene/LuceneSearchEngine.java:3: error: cannot access Field
import static org.apache.lucene.document.Field.Store.YES;
                                        ^
  bad class file: /Users/johnniang/.gradle/caches/modules-2/files-2.1/org.apache.lucene/lucene-core/10.0.0/5a9b3f728041df5b054aaaed3c3fd7ff0fed8ee7/lucene-core-10.0.0.jar(/org/apache/lucene/document/Field.class)
    class file has wrong version 65.0, should be 61.0
    Please remove or make sure it appears in the correct subdirectory of the classpath.

But I'm not sure what will happen after we set minimal Java version to 21, such as whether plugins will work properly.

Additional information

/kind feature
/area core