This is part of removing dependencies from log4j-core so that we only depend on Java 9's java.base in log4j-core.
Move Jackson-based layouts to their own modules:
- log4j-layout-jackson-xml brings in XML specific Jackson jar(s)
- log4j-layout-jackson-yaml brings in YAML specific Jackson jar(s)
The module that holds commons Jackson bits is log4j-layout-jackson.