REFACTOR: revisit registry examples to explore other ways for servicetype aliases

[bsipocz]

Registry searches currently support a few alias terms for servicetype, e.g. 'image' or 'spectra'. However, there is an ongoing discussion of deprecating these.
It would be extremely valuable to do an auditing of the suggested user workflow and whether any of the alternatives would make sense (IMO, I don't think it's realistic to request the beginner users we aim this workshop for to know anything about the individual protocols, especially their different version ,and do registry search for SIA, or SIA2, or SSA, etc.

xref: astropy/pyvo#429

[bsipocz]

One alternative could be: astropy/pyvo#470, we need to check on that from the end user POV

[tomdonaldson]

Further philosophical reference: https://blog.g-vo.org/towards-data-discovery-in-pyvo.html