The catalog table continuous_aggs_bucket_function is currently only used
for variable bucket sizes. Information about the fixed-size buckets is
stored in the table continuous_agg only. This causes some problems
(e.g., we have redundant fields for the bucket_size, fixes size buckets
with offsets are not supported, ...).
This commit is the first in a row of commits that refactor the catalog
for the CAgg time_bucket function. The goals are:
* Remove the CAgg redundant attributes in the catalog
* Create an entry in continuous_aggs_bucket_function for all CAggs
that use time_bucket
This first commit refactors the continuous_aggs_bucket_function table
and prepares it for more generic use. Not all attributes are used yet,
but these will change in follow-up PRs.