Our glossary is stuck in the past, still discussing token ownership in
terms of vnodes and cluster synchronization in terms of gossip.
This patch tries to improve this a bit, although much more work needs to
be done.
The term `Tablet` is added and the definition of `Token` and `Token
Range` is rephrased to be tablet inclusive.
The term `Cluster` is changed to mention raft as the synchronization
mechanism instead of gossip.
One oustanding problem is that our general architecture page describing
the ring acrhitecture is still Vnode only. We have a seprate Tablets
page, but the two don't link to each other and most documentation refer
only to the former. A casual reader might be able to spend a a lot of
time on our documentation page, without even seeing the word: tablets.
Closesscylladb/scylladb#28170
6f5f42305a