Consider removal of msc_* js/wasm standalone transcoder

With the latest updates to the https://github.com/BinomialLLC/basis_universal/ repository, it is possible to decode KTX files (not just `.basis` files) with that transcoder. The msc_* standalone transcoder existed to fill that gap, and mostly represented a mirror of code from that repository otherwise. So I think we should remove the transcoder now, or at least omit it from the next release and from documentation. If we want to keep the build targets around a bit longer for any users who need to migrate (i.e. are depending on the feature in the beta release) that is fine too. Is this OK?

Start by reviewing the msc_* standalone js/wasm transcoder and its build targets, then check where they are referenced in the next release and documentation. Resolve whether the targets should be removed or only omitted from the release and documentation, with migration needs for beta users addressed.

Written by the indexing model from the issue text.