feat: conditionally disable netty unsafe to leverage the ffm api

[derklaro]

Motivation

In netty 4.2.3 a new type of ByteBuffer cleaner (or allocator) will be introduced that uses malloc and free directly using the ffm api on java 24+. In order to enable this cleaner, unsafe has to be unavailable/disabled. Since this can be a performance issue (as the ByteBuffer lifecycle might be controlled by the garbage collector if unsafe is unavailable) we only disable unsafe when the new cleaner implementation is available.

Modification

Add a transformer that checks if all conditions are met to disable unsafe in order to enable the ffm-based cleaner implementation. If that is the case, the PlatformDependent0#explicitNoUnsafeCause0() method will be overridden to always return an UOE to indicate that unsafe is explicitly disabled.

Result

On netty 4.2.3+ unsafe will be disabled in favor of the ffm-linker based cleaner implementation, but only is all necessary preconditions to enable the cleaner are met.

[github-actions]

Test Results

 56 files  ±0   56 suites  ±0   2m 24s ⏱️ -9s
566 tests ±0  566 ✅ ±0  0 💤 ±0  0 ❌ ±0 
931 runs  ±0  931 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 3488619. ± Comparison against base commit e4d1f49.

♻️ This comment has been updated with latest results.