Vacuum bundle to ingest all files in a directory

[nichwall]

Right now, vacuum loads additional files and schemas as they show up in relative references. It would be convenient if the vacuum bundle command had a flag that allowed for using all files to perform the bundle.

The main use case is to allow individual spec files to use local references instead of needing to remember paths to "which file this schema was in" for every reference.

Originally discussed here in Discord where it was said libopenapi already has this functionality, just needs a flag for vacuum. https://discord.com/channels/923258363540815912/1060171609488502784/1223989915600293930