Add ability to rename a tag

[timabell]

Not sure what this should look like

rename subcommand

gitopolis rename-tag oldname newname

pollutes the main subcommand list with trivial detail

rename param

gitopolis tag --rename oldname newname

tidily under the tag subcommand but the old/new is odd

rename param

gitopolis tag --rename oldname --new-name newname

bit like source/destination params, but a lot to type and a bit hard to use

[timabell]

gpt has helped design a command structure that would work
https://chatgpt.com/share/68f17749-c21c-8006-890e-788eaa4f593f

gitopolis rename tag legacy modern --merge
gitopolis move repo services/auth ./apps/auth

To fit nicely with #157 and make use of the fact that subcommands can have their own subcommands in clap (I think)

[timabell]

workaround is to just sed or find-and-replace on the config file