Change default RecylerPool implementation to newLockFreePool (from threadLocalPool)

[cowtowncoder]

With #1089 (and related) completed, Jackson 2.16 both allows for configuring alternate RecyclerPools to use for buffer recycling and provides a set of alternatives, notably ones that do not use ThreadLocal for recycling.

To reduce likelihood of breakage, the default implementation for 2.16 remains ThreadLocal-based pool. This hopefully allows as to gather feedback, experiences by early adopters, on how alternative pools work (for example, Quarkus project is likely to experiment with alternatives). This, in turn, should let us decide on which alternative to use, along with global-vs-per-factory pools.
As the baseline, my icurrent thinking is that per-factory, unbounded/lock-free implementation might work well as the default.

[cowtowncoder]

Ok, to get discussion started, I will propose we will use:

• JsonRecyclerPool.newLockFreePool()

as the default. This will have following benefits:

• Per-factory instances to reduce chance of global contention
• Has low baseline memory usage (for use cases where no recycling occurs)

Potential downside for using non-global/shared pool is that overall memory retention may be higher than with global/shared pools.

As with any choice this will not be the optimal choice for all use cases. I am looking forward to hearing alternative suggestions, comments.

[mariofusco]

Note that this is blocked by FasterXML/jackson-databind#4321

[cowtowncoder]

Note: issue @mariofusco outlined (thanks!) has been resolved now, so the default pool implementation may be changed.