Fix EndpointResolverWithOptions ignored issue

[skmcgrail]

+--------------------------------------+---------+---------+----------+------------------------------------+
|                  ID                  |  TYPE   | MODULES | COLLAPSE |            DESCRIPTION             |
+--------------------------------------+---------+---------+----------+------------------------------------+
| 954dde13-60ef-407d-8ecb-138e35fd6534 | feature |       1 | false    | Add support for specifying         |
|                                      |         |         |          | `EndpointResolverWithOptions`      |
|                                      |         |         |          | on `LoadOptions`, and associated   |
|                                      |         |         |          | `WithEndpointResolverWithOptions`. |
| f0080c1f-15ae-43c5-a697-801297110714 | bugfix  |     301 | true     | Fixes a bug that prevented         |
|                                      |         |         |          | aws.EndpointResolverWithOptions    |
|                                      |         |         |          | from being used by the service     |
|                                      |         |         |          | client.                            |
+--------------------------------------+---------+---------+----------+------------------------------------+

Fixes #1513