Adds a Configuration Converter API (#142)
Adds an API to perform automatic conversions between different logging configuration file formats and a basic implementation.
The implementation supports the following configuration file formats:
- Log4j Core 2 XML,
- Log4j Core 2 JSON,
- Log4j Core 2 YAML,
- Log4j Core 2 Properties (read-only),
- Log4j Core 3 Properties.
The API is extensible through `ServiceLoader` and allows integrators to provide support for additional configuration file formats.
Read-only support for the Log4j 1 Properties and Log4j 1 XML configuration formats will be provided in a separate PR.
**Note**: Currently the API is only accessible from Java code.
Its main purpose is to provide a "Migrate Log4j 1.x to Log4j Core 2.x", a "Migrate Logback to Log4j Core 2.x" and a "Migrate JUL to Log4j Core 2.x" [OpenRewrite recipe](https://docs.openrewrite.org/recipes/java/logging/log4j).
A `picocli`-based `log4j-transform-cli` tool to access all the goodies in this repository, will be provided later.
Closes apache/logging-log4j2#2080
45 files changed
