Implement ALTER schema for changing schema location

[marton-bod]

Once a schema has been created with the wrong default location, it is currently not possible to change its location after creation time. This can be a problem, especially when dropping and recreating the schema is no longer an option, because several tables have already been created in the schema.

Once a mistake has been made with the schema location (e.g. the schema default location points to the local filesystem), all subsequent table creations in this schema will require explicitly specifying the location property (otherwise they would fail), and MV creations will also require setting the schema_name property to point to some other schema.

It should be made possible to change the default location of a schema using ALTER schema command to help rectify these situations.

[legiondean]

This feature will be super helpful for maintenance.