Applies to all instances of the vulnerability lists.
The MR and pipelines pages and both the project and group security
dashboards.

- Adds actions and mutations for creating an MR to the GSD store
- Adds actions and mutations for creating an MR to the reports store
- Adds a `<split-button>` component
- Adds an `<event-item>` component
- Adds support for the new remediations syntax
- Fixes up all the failing tests
- Adds new tests for the new components and functionality