Split direct/transitive dependencies in two groups in outdated command

[Seldaek]

Fixes #10447

Before:

Color legend:
- patch or minor release available - update recommended
- major release available - update possible
doctrine/common                   3.2.2            3.3.0            PHP Doctrine Common project is a library that provides additional functionality that other Doctrine projects...
doctrine/data-fixtures            1.5.2            1.5.3            Data Fixtures for all Doctrine Object Managers
doctrine/dbal                     3.3.4            3.3.6            Powerful PHP database abstraction layer (DBAL) with many features for database schema introspection and mana...
doctrine/deprecations             v0.5.3           v1.0.0           A small layer on top of trigger_error(E_USER_DEPRECATED) or PSR-3 logging with options to disable all deprec...
doctrine/doctrine-bundle          2.6.0            2.6.3            Symfony DoctrineBundle
doctrine/doctrine-fixtures-bundle 3.4.1            3.4.2            Symfony DoctrineFixturesBundle
doctrine/orm                      2.11.2           2.12.2           Object-Relational-Mapper for PHP

After:

$ c outdated
Color legend:
- patch or minor release available - update recommended
- major release available - update possible

Direct dependencies:
doctrine/common                   3.2.2            3.3.0            PHP Doctrine Common project is a library that provides additional functionality that other Doctrine projects...
doctrine/doctrine-bundle          2.6.0            2.6.3            Symfony DoctrineBundle
doctrine/doctrine-fixtures-bundle 3.4.1            3.4.2            Symfony DoctrineFixturesBundle
doctrine/orm                      2.11.2           2.12.2           Object-Relational-Mapper for PHP

Transitive dependencies:
doctrine/data-fixtures            1.5.2            1.5.3            Data Fixtures for all Doctrine Object Managers
doctrine/dbal                     3.3.4            3.3.6            Powerful PHP database abstraction layer (DBAL) with many features for database schema introspection and mana...
doctrine/deprecations             v0.5.3           v1.0.0           A small layer on top of trigger_error(E_USER_DEPRECATED) or PSR-3 logging with options to disable all deprec...
doctrine/persistence              2.4.1            3.0.2            The Doctrine Persistence project is a set of shared interfaces and functionality that the different Doctrine...

Using --direct removes the grouping/header as it shows only direct dependencies then.