[std.orogen] adopt to renamed "struct metadata::ComponentDescription"

Related to (this)[https://github.com/rock-core/tools-orogen_metadata/pull/2] PR.

What about the `make_orogen_metadata_optional` branch? Its in rock1408, but not in master? And commit-msg states it should not be released...? *scratch*

Signed-off-by: Martin Zenzes <martin.zenzes@dfki.de>