OF-3136: Remove deprecated code
This removes code that has been marked for removal in version 5.1.0 of Openfire, in addition to earlier removals done in commit a8ee1b6dc9045fe6f0b64bc893335eb0f07e1a9b
IQMuclumbusSearchHandler was unmarked for immediate removal, as its only known user (search.jabber.network) is still using it.
ci: replace sleep-based synchronization with deterministic wait in ArchiverTest
testArchiverInDistinctBatchesWhenOutsideGrace used Thread.sleep() to ensure the archiver had flushed the first item before submitting the second. This relied on the OS thread scheduler waking the archiver thread within the sleep window, which holds on Linux but not on macOS due to differences in thread scheduling behavior between the two platforms.
Replace the sleep with the existing waitUntilArchivingIsDone() helper, which polls until the first item is confirmed stored before archiving the second. This makes the test deterministic regardless of platform or scheduler behavior.
CI: Add Java 25
Java 25 is a long-term support release (September 2025). This makes it likely that users will use it to run Openfire. It should therefor be added to our integration test matrix.
