Add Family collection to cat.Table. This information will be used by the
Update column pruning code.

Release note: None

Previously, the list of RETURNING columns was inferred for mutation
operators. However, in order to make pruning of input columns easier, and
to prepare for a future when ReturnCols can be pruned, this commit makes
the list explicit.

For now, the new ReturnCols list is never pruned. Additional execution
support is required for that.

Release note: None

Prune input columns that are not needed by Update and Upsert operators.
Needed columns include returned columns and columns needed to formulate
KV Put and Delete operations to implement the mutations. All other
columns can be pruned.

This commit contains new code to enable the Upsert fast path with the
CBO. The fast path uses the KV Put method to blindly insert new rows
or overwrite existing rows. Because any existing data is ignored, it is
not necessary to fetch existing rows, as is normally required. This
also allows a much simpler logical plan.

After this change, the optimizer updates/upserts no longer need to stay
behind a feature flag, as all fast paths should now work at least as
well as they do with the heuristic planner.

Release note (sql change): Delete, Update, and Upsert statements are
now planned by the cost-based optimizer.

Release note: None