Fix BOM packaging in consumer POMs (#11427)

This commit addresses two issues with BOM (Bill of Materials) handling in consumer POMs:

1. BOM packaging not transformed to POM in consumer POMs:
   When a project uses packaging=bom, the consumer POM was incorrectly
   retaining this packaging type. Since 'bom' is not a valid packaging
   type in Maven 4.0.0 model, this caused errors when the consumer POM
   was used. The fix ensures that BOM packaging is always transformed
   to 'pom' in consumer POMs, regardless of whether flattening is enabled.

2. Dependency versions preserved in dependencyManagement:
   The effective model already contains resolved versions for dependencies
   in dependencyManagement sections. The fix ensures these versions are
   properly preserved in the consumer POM for both flattened and
   non-flattened BOMs.

Changes:
- Modified DefaultConsumerPomBuilder.build() to detect BOMs based on
  original packaging and handle them appropriately
- Added buildBomWithoutFlatten() method to handle BOMs when flattening
  is disabled, using the raw model but still transforming packaging
- Added integration test to verify both issues are fixed

Fixes issues reported in:
https://lists.apache.org/thread/41q40v598pd8mr32lmgwdfb2xm7lzm6l