Remove sun.misc.Unsafe memory access API usage

[mbien]

JDK 26 or later will throw an exception whenever a memory-access method from the Unsafe class is used (JEP 498). JDK 24 will log warnings to console.

nb 25 started on JDK 24 in terminal will print the following to console:

WARNING: A terminally deprecated method in sun.misc.Unsafe has been called
WARNING: sun.misc.Unsafe::objectFieldOffset has been called by com.google.common.util.concurrent.AbstractFuture$UnsafeAtomicHelper (jar:file:/home/mbien/dev/nb/java/maven/lib/guava-33.2.1-jre.jar!/)
WARNING: Please consider reporting this to the maintainers of class com.google.common.util.concurrent.AbstractFuture$UnsafeAtomicHelper
WARNING: sun.misc.Unsafe::objectFieldOffset will be removed in a future release

(but there might be more usages, guava might have it fixed in the next release google/guava#6806 (comment))