sql/schemachanger: enable declarative CREATE SEQUENCE

Previously, CREATE SEQUENCE was disabled in the declarative
schema changer because we were missing sufficient test coverage
and not comfortable enabling it by default. This patch enables,
CREATE SEQUENCE in the declarative schema changer again.

Release note (sql change): CREATE SEQUENCE is now enabled by default in
the declarative schema changer.

pkg/sql/logictest/testdata/logic_test/new_schema_changer

@@ -1523,16 +1523,16 @@ EXPLAIN (DDL) ALTER TABLE stmt_ctrl ADD COLUMN j BOOL
 statement ok
 ALTER TABLE stmt_ctrl ADD COLUMN fallback_works BOOL
 
-# Validate that CREATE SEQUENCE is disabled and can be re-enabled with the same flag.
+# Validate that CREATE SCHEMA is disabled and can be re-enabled with the same flag.
 statement error pgcode 0A000 cannot explain a statement which is not supported by the declarative schema changer
-EXPLAIN (DDL) CREATE SEQUENCE sq2
+EXPLAIN (DDL) CREATE SCHEMA schema1
 
 statement ok
-SET CLUSTER SETTING sql.schema.force_declarative_statements='+CREATE SEQUENCE'
+SET CLUSTER SETTING sql.schema.force_declarative_statements='+CREATE SCHEMA'
 
 skipif config local-mixed-23.1
 statement ok
-EXPLAIN (DDL) CREATE SEQUENCE sq2
+EXPLAIN (DDL) CREATE SCHEMA sc1
 
 subtest end
 

pkg/sql/schemachanger/scbuild/internal/scbuildstmt/process.go

@@ -65,7 +65,7 @@ var supportedStatements = map[reflect.Type]supportedStatement{
 	reflect.TypeOf((*tree.DropRoutine)(nil)):         {fn: DropFunction, statementTags: []string{tree.DropFunctionTag, tree.DropProcedureTag}, on: true, checks: nil},
 	reflect.TypeOf((*tree.CreateRoutine)(nil)):       {fn: CreateFunction, statementTags: []string{tree.CreateFunctionTag, tree.CreateProcedureTag}, on: true, checks: nil},
 	reflect.TypeOf((*tree.CreateSchema)(nil)):        {fn: CreateSchema, statementTags: []string{tree.CreateSchemaTag}, on: false, checks: isV232Active},
-	reflect.TypeOf((*tree.CreateSequence)(nil)):      {fn: CreateSequence, statementTags: []string{tree.CreateSequenceTag}, on: false, checks: isV232Active},
+	reflect.TypeOf((*tree.CreateSequence)(nil)):      {fn: CreateSequence, statementTags: []string{tree.CreateSequenceTag}, on: true, checks: isV241Active},
 	reflect.TypeOf((*tree.CreateDatabase)(nil)):      {fn: CreateDatabase, statementTags: []string{tree.CreateDatabaseTag}, on: true, checks: isV241Active},
 }