Detect dependencies duplicates in <dependenciesManagement> section

[alexey-anufriev]

Currently, enforcer works only over <dependencies> section, but this is not always convenient, for example, to publish a BOM (that defines dependencies in <dependenciesManagement>) being sure about dependencies there is a need to explicitly use those in <dependencies> section, otherwise, they will not be scanned. This may lead to unnecessary workarounds, like making a separate module with explicit dependencies that can be scanned.

Instead, it would be more convenient to perform a scan over the section.