Use nip22 style tags in git statuses

[dluvian]

Replace markers with nip22 style tags

@DanConwayDev @TheAwiteb

[TheAwiteb]

LGTM

[DanConwayDev]

Concept ACK.
Imo the old tags should remain in the nip but be marked as depricated.
It should also be highlighted that this is a breaking change.
Gitworkshop and ngit both have support for fetching and associating statuses using this style. I can trivially switch them to issuing new statuses using this style as the nip is merged.
It also raises the question whether we should also switch to NIP-22 for patches.
I wrote #1799 which switched all nip34 events to NIP-22.
With the introduction of PRs in #1966 perhaps we have an opportunity to batch a bunch of these breaking changes together.