Add process-package lifecycle phase

There are multiple "post processing" plugins that take a created artifact (such as a jar file) and post-process it. Today, the order of e.g. the jar plugin and the shade plugin is purely determined by the order that they appear in the pom file, making this process brittle.

The default maven lifecycle has a number of steps with "pre" and "post" phases, e.g. integration-test has "pre-integration-test" and "post-integration-test" or at least "post" phases (e.g. process-sources, process-classes, process-test-classes etc.).

The proposal is to add a new lifecycle phase for either Maven 3.9.x or Maven 4.0 which is called "process-package", analog to the process phases above that slots in after "package" and before "pre-integration-test".  Running "mvn package" would execute the lifecycle up to and including this phase.