Because LWT isn't yet implemented with tablets (#18068) and because we considered LWT an important part of Alternator, after c24bc3b the Alternator CreateTable operation defaults to creating a table using vnodes, not tablets.

We should document this fact (perhaps in docs/alternator/new-apis.md), and also document the experimental:initial_tablets tag that can be added during CreateTable to override this default. We should also document what the contents of this tag means (we have a few tests for it and comments in the code that explain it).

Finally, we should explain what are the current limitations when creating an Alternator table with tablets explicitly turned on:

1. Alternator Streams won't work for this table (GA Alternator Streams #16367). An attempt to turn it on during table creation or later will result in a clear error message.
2. TTL won't work for this table (Support tablets in Alternator TTL #16567). Again, an attempt to turn it on will result in a clear error message.
3. Writes that need LWT won't work. If I remember correctly, the error won't come when setting the write isolation mode (the --alternator-write-isolation configuration or the system:write_isolation tag) to the "bad" values always_use_lwt or only_rmw_uses_lwt, but the writes themselves will fail. But I need to confirm that in a test.