CLI: mcap info should display the file size

[wkalt]

The rosbag info command has these compression listings:

compression:  lz4 [705/705 chunks; 71.48%]
uncompressed: 679.4 MB @ 35.5 MB/s
compressed:   485.6 MB @ 25.4 MB/s (71.48%)

We have the first, but not the other two. I assume those are computed from chunk statistics, which we could also do.