[YSQL] Add support for ALTER SEQUENCE

[hectorgcr]

Currently we can create and delete a sequence but we cannot alter it.

This is especially important for our sequences implementation because we want users to not use SERIAL types but instead its equivalent using a large value for CACHE:

CREATE SEQUENCE tablename_colname_seq CACHE 100000;
CREATE TABLE tablename (
    colname integer NOT NULL DEFAULT nextval('tablename_colname_seq')
);
ALTER SEQUENCE tablename_colname_seq OWNED BY tablename.colname;

[lukaseder]

The requested syntax should be possible by now, see: https://docs.yugabyte.com/latest/api/ysql/the-sql-language/statements/ddl_alter_sequence/

But this issue is still being referenced when attempting to rename a sequence using:

ALTER SEQUENCE s1 RENAME TO s2;

[OlegLoginov]

As I see the feature implements the following sub-set of ALTER SEQUENCE s SeqOptElem commands:

SeqOptElem:		  AS SimpleTypename
			| CACHE NumericOnly
			| CYCLE
			| NO CYCLE
			| INCREMENT opt_by NumericOnly
			| MAXVALUE NumericOnly
			| MINVALUE NumericOnly
			| NO MAXVALUE
			| NO MINVALUE
			| OWNED BY any_name
			| SEQUENCE NAME_P any_name
			| START opt_with NumericOnly
			| RESTART
			| RESTART opt_with NumericOnly

Other ALTER SEQUENCE sub-commands are not supported yet.