Further isolate legacy dependencies from current ones

The dependencyManagement in main still isn't clean enough. The bom used for Preview depends on the bom used for std WF, which masks the fact that the wildfly-ee-feature-pack-parent pom includes items that are not specific to std WF (i.e. are used in WFP) and that the root pom includes items that are not shared between std WF and WFP.

This interferes with WFLY-16652 by preventing providing a consistent dependency set to the std WF feature pack modules when I try and move them over to the EE 10, etc dependencies.

To resolve this I intend to create a boms folder in the source tree, with 6 child maven modules

common-ee
common-expansion
legacy-ee
legacy-expansion
preview-ee
preview-expansion
standard-ee
standard-expansion

'ee' vs 'expansion' relates to whether the boms are used for FPs that don't provide expansion capabilities like MP.

'common' is for things shared between the others.
'preview' is for deps specific to WFP
'standard' is for deps specific to std WF
'legacy' are for things not used in FPs but still used for things like compilation of legacy (javax) maven modules. This will initially be empty.

Work for this JIRA will initially set these up. Part of WFLY-16652 will be to then move the dependencyManagement items from 'standard' to 'legacy' and then from 'preview' to 'standard'.