spanner: Allow RENAME TABLE and ALTER TABLE ... RENAME TO in the parser

[killah777]

Is your feature request related to a problem? Please describe.

The go client currently rejects RENAME TABLE ... TO and ALTER TABLE ... RENAME TO, but Spanner will soon support the syntax.
In addition, SYNONYM will also be supported for graceful table renaming. This adds DDL statements such as CREATE TABLE (... SYNONYM (name)), ALTER TABLE ... ADD SYNONYM ..., and ALTER TABLE ... DROP SYNONYM ....

Describe the solution you'd like
Allow RENAME TABLE ... TO, ALTER TABLE ... RENAME TO, CREATE TABLE (... SYNONYM (name)), ALTER TABLE ... ADD SYNONYM ..., and ALTER TABLE ... DROP SYNONYM ... in the ddl parser.

Describe alternatives you've considered
N/A

Additional context
N/A