schema: for NWB files identify and list NWB extensions "included" and their versions

NWB extensions are somewhat of a weak point of NWB: their code lives outside, PyNWB could introduce breakages etc. I have recommended to establish "downstream" testing (https://github.com/NeurodataWithoutBorders/pynwb/issues/1338) to assist in not rendering nwb files non-loadable. But complimentary to that I think it would benefit us and DANDI users to know what extensions are contained in any given nwb file, e.g. ATM I would like to know which dandisets in the archive have nwb files **without** extensions so I have a better chance to have them load.
We already have an ad-hoc way to detect and autoload some (https://github.com/dandi/dandi-cli/blob/ea86eeee974fc58fac03b0af86cf606baba06e97/dandi/metadata.py#L68) which could provide a starting point. I guess it should be an additional entry within `asset.wasGeneratedBy` which would list the extension and its version. Right @satra?

@bendichter is there a better than our ad-hoc way to identify if file "has extensions" in it? (I asked a related question in https://github.com/NeurodataWithoutBorders/pynwb/issues/1337 but it might actually be even pertinent to nwb-schema itself)