Rename "name" and "abbreviation" fields in TOML fedora block

As documented in TEMPLATE.toml, currently we have an optional [fedora] block that includes the fields "name" and "abbreviation". I believe the terminology here is confusing and I've made a few changes to the comments in TEMPLATE.toml to try to make this clearer. However, I think we should go further and use clearer names for these fields.

Particularly with respect to the short names: Since Fedora has adopted the use of SPDX expressions and is essentially deprecating use of the previous system that we have often been calling "Callaway", we shouldn't give the impression that there are at present non-SPDX-conformant "Fedora" short names.

I propose "legacy-name" instead of "name" and "legacy-abbreviation" or "callaway-name" for "abbreviation". Or something similar to those.