fixes: #7156 - Adds support for PostgreSQL MultiRange type

fixes: #7156 - Adds support for PostgreSQL MultiRange type

This adds functionality for PostgreSQL MultiRange type, as discussed in Issue #7156.

As far as I can tell, only psycopg provides a [Multirange adaptation](https://www.psycopg.org/psycopg3/docs/basic/pgtypes.html#multirange-adaptation). Psycopg2 only supports a [Range adaptation/data type](https://www.psycopg.org/psycopg3/docs/basic/pgtypes.html#multirange-adaptation).

This pull request is:

- [ ] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [ ] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [x] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

Closes: #7816
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/7816
Pull-request-sha: 7e9e0c858dcdb58d4fcca24964ef8d58d1842d41

Change-Id: I345e0f58f534ac37709a7a4627b6de8ddd8fa89e