Remove prefixes from all the *CoordinateSystem metadata fields?

[yarikoptic]

Came up during BEP032 discussion, that for every modality there is an addition of CoordSysType prefix as e.g. in https://bids-specification.readthedocs.io/en/stable/appendices/coordinate-systems.html#eeg-specific-coordinate-systems .

But due to separation of datatypes into separate folders, it is unclear why such prefix is generally needed to avoid some collisions.