Add support for MR title/description regex
The create and update project API endpoints should accept the following attributes:
- `merge_request_title_regex`
- `merge_request_title_regex_description`
However, they are not documented on the website, only in the OpenAPI spec: https://gitlab.com/gitlab-org/gitlab/-/blob/master/doc/api/openapi/openapi_v3.yaml?ref_type=heads
We need to verify whether they can be set on the two endpoints or not, then if they can, to add support here.
## Implementation Guide
- Follow the `CONTRIBUTING.md` guide for setting up your local development environment.
- Clone the community fork of this project.
- Add the two new attributes to structs `CreateProjectOptions`, `EditProjectOptions` and `Project` in `projects.go`.
- Create an integration test to ensure the attributes can be used to create and update projects.
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