Add Remediation type for Security Report Findings

What does this MR do and why?

This MR adds the remediations field to the PipelineSecurityReportFinding graphQL type used in the securityReportFinding(s) field.

Screenshots or screen recordings

How to set up and validate locally

Test query on security finding with a remediation (Example Project):

query {
  project(fullPath:"<project path>") {
    pipeline(iid:"<pipeline iid>") {
      securityReportFinding(uuid:"<uuid>") {
        remediations {
          summary
          diff
        }
      }
    }
  }
}

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #384508 (closed)