Implement SetRunnerAssociatedProjectsService

What does this MR do and why?

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This MR adds the SetRunnerAssociatedProjectsService which is a more capable version of AssignRunnerService/UnassignRunnerService services. SetRunnerAssociatedProjectsService can take an array of projects and add/remove projects as needed so that the final list of projects associated with a runner is as specified. This will be used in the runnerUpdate mutation later on.

Part of GraphQL API: Extend `runnerUpdate` mutation to ... (#359958 - closed)

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