[Feature request] Open multiple bagfiles as one

[Timple]

tldr: Open multiple bagfiles as if it was one

There is a nice option to open multiple bagfiles and they all get namespaced. I find myself in the position of having multiple sequential bagfiles (--split option). It would be nice if we can load them without the namespacing because it's the same data.

This has some implications:

• Bagfiles may overlap (might simply be ignored)
• Bagfiles may not contain same data (difficult for selection options)

Opening this here instead of the ros plugins repo as it might be relevant for csv files or others as well.