sql: Added CREATE SEQUENCE AS <typename> option.

Previously, unimplementedWithIssueDetail error was thrown
when an AS option in CREATE SEQUENCE ... AS was encountered.

Now we support the AS option for creating sequences which can
take on values such as smallint/integer/bigint. Typically (i.e.
in Postgres) the AS option allows users to specify an integer
type, which dictates the min and max integer values a sequence
can take on. Before this change, the only option value we supported was
bigint/int8/int/integer, which corresponds to our default
min and max values for sequences.

NB: In postgres, `integer` corresponds to int4. In cockroach, we use
`nakedIntType` which defaults to int8 but can be configured in the
cluster settings.

Release note (sql change): Added CREATE SEQUENCE AS <typename> option.

docs/generated/sql/bnf/alter_sequence.bnf

@@ -1,5 +1,5 @@
 alter_sequence_stmt ::=
 	( 'ALTER' 'SEQUENCE' sequence_name 'RENAME' 'TO' sequence_name | 'ALTER' 'SEQUENCE' 'IF' 'EXISTS' sequence_name 'RENAME' 'TO' sequence_name )
-	| ( 'ALTER' 'SEQUENCE' sequence_name ( ( ( 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) ( ( ( 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) )* ) | 'ALTER' 'SEQUENCE' 'IF' 'EXISTS' sequence_name ( ( ( 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) ( ( ( 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) )* ) )
+	| ( 'ALTER' 'SEQUENCE' sequence_name ( ( ( 'AS' typename | 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) ( ( ( 'AS' typename | 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) )* ) | 'ALTER' 'SEQUENCE' 'IF' 'EXISTS' sequence_name ( ( ( 'AS' typename | 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) ( ( ( 'AS' typename | 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) )* ) )
 	| ( 'ALTER' 'SEQUENCE' sequence_name 'SET' 'SCHEMA' schema_name | 'ALTER' 'SEQUENCE' 'IF' 'EXISTS' sequence_name 'SET' 'SCHEMA' schema_name )
 	| ( 'ALTER' 'SEQUENCE' sequence_name 'OWNER' 'TO' role_spec | 'ALTER' 'SEQUENCE' 'IF' 'EXISTS' sequence_name 'OWNER' 'TO' role_spec )

docs/generated/sql/bnf/create_sequence_stmt.bnf

@@ -1,3 +1,3 @@
 create_sequence_stmt ::=
-	'CREATE' opt_temp 'SEQUENCE' sequence_name ( ( ( ( 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) ( ( ( 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) )* ) |  )
-	| 'CREATE' opt_temp 'SEQUENCE' 'IF' 'NOT' 'EXISTS' sequence_name ( ( ( ( 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) ( ( ( 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) )* ) |  )
+	'CREATE' opt_temp 'SEQUENCE' sequence_name ( ( ( ( 'AS' typename | 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) ( ( ( 'AS' typename | 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) )* ) |  )
+	| 'CREATE' opt_temp 'SEQUENCE' 'IF' 'NOT' 'EXISTS' sequence_name ( ( ( ( 'AS' typename | 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) ( ( ( 'AS' typename | 'NO' 'CYCLE' | 'OWNED' 'BY' 'NONE' | 'OWNED' 'BY' column_name | 'CACHE' integer | 'INCREMENT' integer | 'INCREMENT' 'BY' integer | 'MINVALUE' integer | 'NO' 'MINVALUE' | 'MAXVALUE' integer | 'NO' 'MAXVALUE' | 'START' integer | 'START' 'WITH' integer | 'VIRTUAL' ) ) )* ) |  )

docs/generated/sql/bnf/stmt_block.bnf

@@ -2650,7 +2650,8 @@ alter_index_cmd ::=
 	partition_by_index
 
 sequence_option_elem ::=
-	'NO' 'CYCLE'
+	'AS' typename
+	| 'NO' 'CYCLE'
 	| 'OWNED' 'BY' 'NONE'
 	| 'OWNED' 'BY' column_path
 	| 'CACHE' signed_iconst64