Disable programmatic configuration if `log4j1.compatibility` is `false` (LOG4J2-3467)

[ppkarwasz]

This issue is moved from the LOG4J2-3467 JIRA issue.

The log4j-1.2-api artifact is a bridge, whose main purpose is to forward Log4j 1 "API" calls to Log4j 2 API.

Version 2.17.2 of the artifact introduced support for configuring Log4j Core using the Log4j 1 PropertyConfigurator and DOMConfigurator classes.
This feature should be disabled by default and depend on the opt-in log4j1.compatibility property, because:

• many third-party libraries (not related to logging) take upon themselves the reconfiguration of Log4j 1. This steals the control of logging configuration from application developers (see How to disable log4j programmatic reconfiguration from a 3rd party jar for example).
• if some applications actually use those classes, they can always set log4j1.compatibility to true. This configuration property is also used to enable the scanning of the classpath for log4j.properties and log4j.xml files.

[garydgregory]

Sounds reasonable. This should be front-and-center in the release notes in a MINOR release, not a MAINTENANCE release as it is an important behavior breaking change.