chore: add MAINTAIN support for postgres >= 17

[sudo-dliberty-eiq]

The MAINTAIN privilege was added in Postgres 17.
https://www.postgresql.org/docs/17/ddl-priv.html

This change adds support for users on Postgres 17, however, opening up means users of this provider attempting to add MAINTAIN permissions on databases <= 17 will get an error.

This change addresses this issue:
#506

This pull request includes changes to the postgresql/helpers.go and postgresql/helpers_test.go files to add the new "MAINTAIN" privilege for tables. The most important changes are as follows:

Privileges update:

• postgresql/helpers.go: Added "MAINTAIN" to the list of allowed privileges for tables.

Test updates:

• postgresql/helpers_test.go: Updated the test case in TestArePrivilegesEqual to include the "MAINTAIN" privilege.

[chafouin]

Hello ! Do you think it would be possible to get a release of the provider soon with this PR merged ? That would help us to get unblocked as we are trying to add the MAINTAIN to permission to some of our users. Thanks !