feat: Use Linkset for anchor

[bstasyszyn]

Change the anchor model to remove AnchorEvent from anchor data that is persisted and instead use Linksets. The AnchorEvent is only used for wrapping the Linkset in Create and Announce activities.

closes #1145

Signed-off-by: Bob Stasyszyn Bob.Stasyszyn@securekey.com

[codecov]

Codecov Report

Merging #1180 (c1dabb0) into main (bbae2bf) will decrease coverage by 0.32%.
The diff coverage is 81.32%.

@@            Coverage Diff             @@
##             main    #1180      +/-   ##
==========================================
- Coverage   88.63%   88.30%   -0.33%     
==========================================
  Files         171      171              
  Lines       16883    16831      -52     
==========================================
- Hits        14964    14863     -101     
- Misses       1204     1239      +35     
- Partials      715      729      +14     

Impacted Files	Coverage Δ
pkg/activitypub/store/spi/spi.go	25.00% <ø> (ø)
pkg/activitypub/vocab/util.go	83.33% <ø> (+7.26%)	⬆️
pkg/activitypub/vocab/vocab.go	100.00% <ø> (ø)
.../anchor/anchorlinkset/vcresthandler/resthandler.go	89.65% <ø> (ø)
pkg/store/anchorstatus/store.go	96.51% <ø> (ø)
...tivitypub/service/activityhandler/outboxhandler.go	76.38% <50.00%> (-2.98%)	⬇️
pkg/hashlink/hashlink.go	90.90% <50.00%> (-2.89%)	⬇️
pkg/anchor/anchorlinkset/anchorlinkset.go	62.63% <62.63%> (ø)
...ctivitypub/service/activityhandler/inboxhandler.go	83.16% <66.23%> (-1.20%)	⬇️
cmd/orb-server/startcmd/start.go	71.20% <66.66%> (-0.46%)	⬇️
... and 36 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bbae2bf...c1dabb0. Read the comment docs.