Store ROS_DISTRO as metadata.yaml and in the storage file

[wkalt]

Description

I recently discovered that ros2 db3 bag files recorded by different versions of ROS can have different database schemas. For example, bags recorded on eloquent do not have the offered_qos_profiles column in the topics table, which caused our (Foxglove's) db3 to mcap converter to fail on eloquent bags.

It would be helpful if the ros2 bag recorder wrote its ROS version to the db3 file, to enable consumers to cleanly dispatch to different parsing behavior.

Implementation Notes / Suggestions

Perhaps a new table like "metadata" or some similar concept.