Resolve Vulnerabilities::StarboardVulnerabilityCreateService cross transaction issues

What does this MR do and why?

This MR removes the cross DB interaction suppresion from the described service as part of the sec-decomposition and remediates the code to work post decomposition. This required updates to the cluster_agents and projects tables to be moved out of the transaction as those updates will go to the main DB as averse to the Sec DB.

This does carry the unfortunate theoretical consequence that information could theoretically desyncronize if there is a failure after the execution of the initial transaction, unlikely as that is. We are currently considering implementing data consistency checks to fix problems like these should they arise.

MR acceptance checklist

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Related to #476584 (closed)