read mcap files without the metadata.yml

[tgoelles]

Support for mcap files without metadata.yml files.

Pointcloudset used rosbags package to read mcap files, which currently does not support reading without the metadata.

see also https://gitlab.com/ternaris/rosbags/-/issues/78

I only need pointcloud2

Possible solution

• on the fly generation of metadata.yml and then just use rosbags
• use of low level functions of rosbags and avoud metadata.yml all to gether
• use of other library to read
• maybe use ros2 bag reindex to generate it
• use rosbag2_py to reindex it

[tgoelles]

Current solution is to wait for rosbags to implement this. The workarround is to reindex with the mcap CLI tool