Update dependency org.jctools:jctools-core to v4.0.6 (branch_9x)

[solrbot]

This PR contains the following updates:

Package	Type	Update	Change
org.jctools:jctools-core (source)	dependencies	patch	4.0.5 -> 4.0.6

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Release Notes

JCTools/JCTools (org.jctools:jctools-core)

v4.0.6: Add VarHandle queues and other minor fixups

NOTE: This will be the last release with JDK6 bytecode for jctools-core. The next release will be 5.0.0 and will compile with the 1.8 target, allowing for method handles.

This release has 2 artifacts. The old jctools-core with the following changes:

• Where plain access to field is used by queues, the field is not volatile and volatile access is done using Unsafe.
• Use a generated ConcurrentCircularXXXQueue instead of hand rolled base classes in generated code.
• Padding blocks formatting is improved in generated code.

The release introduces a new artifact, jctools-core-jdk11 which included generated VarHandle queues (padded and unpadded). These queues do not rely on Unsafe, and offer better performance than the AtomicFieldUpdater generated code. We expect many users will prefer these variants going forward to break their reliance on Unsafe.

The majority of the VarHandle work is a great contribution from @​amarziali , thanks!!!
We also thank @​franz1981 for his help reviewing and profiling the code.

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