Add argument to GraphQL VR input type

This MR adds an argument, Global ID of the merge request where resolution will be provided as a suggestion, to the existing mutation ResolveVulnerabilityInputType.

From POC Draft: End-to-end spike for suggest vulnerabili... (!164555 - closed) • Darby Frey, it was decided that new mutation was not needed and it will suffice to add only argument to the existing mutation. The required service changes needed for the argument will be done as part of LLM completion to resolve vulnerability from MR (#481537 - closed) • Subashis Chakraborty • 17.5.

Related to #481535 (closed)