Reduce duplication between `CREATE TABLE` and `ADD COLUMN` SQL conversion #2847

Job	Run time
test (pg: 14.8, schema: public)	1m 22s
test (pg: 14.8, schema: non_public)	1m 24s
test (pg: 15.3, schema: public)	1m 22s
check ledger	3s
dead code check	58s
test (pg: 15.3, schema: non_public)	1m 17s
cross-platform build	2m 55s
test (pg: 16.4, schema: public)	1m 22s
lint	15s
type generation	23s
test (pg: 16.4, schema: non_public)	1m 21s
test (pg: 17.0, schema: public)	1m 17s
test (pg: 17.0, schema: non_public)	1m 18s
examples (pg: 14.8, schema: public)	1m 7s
test (pg: latest, schema: public)	1m 28s
validate examples JSON	7s
examples (pg: 14.8, schema: non_public)	1m 19s
test (pg: latest, schema: non_public)	1m 20s
examples (pg: 15.3, schema: public)	1m 12s
examples (pg: 15.3, schema: non_public)	1m 8s
license check	5s
examples (pg: 16.4, schema: public)	1m 8s
examples (pg: 16.4, schema: non_public)	1m 11s
examples (pg: 17.0, schema: public)	1m 21s
examples (pg: 17.0, schema: non_public)	1m 11s
examples (pg: latest, schema: public)	1m 8s
examples (pg: latest, schema: non_public)	1m 8s
release	0s
	30m 10s

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