mvn-scalaxb: Move invoker plugin configuration in POM to pluginManagement.
mvn-scalaxb: Move invoker plugin configuration in POM to pluginManagement.

Move the invoker plugin configuration out of the `it` profile, and change
execution id to 'default-cli'. This allows integration tests to be run
directly with `mvn invoker:run`.

Banno/scalaxb,Banno/scalaxb,Fayho/scalaxb,Fayho/scalaxb,briantopping/scalaxb,justjoheinz/scalaxb,Fayho/scalaxb,briantopping/scalaxb,justjoheinz/scalaxb,eed3si9n/scalaxb,Banno/scalaxb,eed3si9n/scalaxb,eed3si9n/scalaxb,justjoheinz/scalaxb,briantopping/scalaxb