Merge queue factory interfaces

[ppkarwasz]

Right now there are multiple interfaces with a similar purpose in main:

• QueueFactory,
• QueueFactories.BoundedQueueFactory,
• BlockingQueueFactory.

I believe we should merge them into a single interface.

We should also move the two implementations of BlockingQueueFactory that depend on JCTools and Conversant Disruptor into their own modules. Since these implementations can be used in both log4j-api and log4j-core they should:

• be accessible via ServiceLoader and configurable via Log4j properties,
• be annotated as Log4j Plugins and configurable as Log4j plugins.

[ppkarwasz]

The QueueFactory interface might have external implementations, but it is independent of logger, so I would put it in spi or even better queue, spi.queue or queue.spi. Putting it in a separate package would give a clear signal that it is a separate SPI.

Hibernate 5.x (cf. Javadoc) did a major refactoring and put all optional services in separate foo.spi packages. Using their convention o.a.l.l.queue.spi sound the best.

[vy]

This issue is (mostly) fixed by #2104:

• QueueFactories and QueueFactory are removed
• BlockingQueueFactory is left in log4j-core with a JCTools-based implementation in the new log4j-jctools module