Update compliance report local resolver to match new format

What does this MR do and why?

This MR is part of a series of changes to update the compliance report to consume the newly added GraphQL endpoint #342897 (closed):

1. Update compliance report local resolver to match new format. 👈 You are here.
2. Update the compliance report to use the new GraphQL endpoint. !82397 (merged)

Changes made to the format:

• severity is now severityLevel
• severityLevel and reason will return the enum text not the enum int e.g. CRITICAL rather than 4
• mergedBy is now mergeUser
• reference is now ref
• project has been moved to mergeRequest.project
• createdBefore/createdAfter are now mergedBefore/mergedAfter: https://docs.gitlab.com/ee/api/graphql/reference/#complianceviolationinput
• SEVERITY_ASC/DESC is now SEVERITY_LEVEL_ASC/DESC: https://docs.gitlab.com/ee/api/graphql/reference/#complianceviolationsort

This feature is behind a development feature flag.

Screenshots or screen recordings

No visual change.

Screen_Recording_2022-03-08_at_14.23.58

How to set up and validate locally

1. You need a GitLab Ultimate license.
2. Enable the new feature flag in your terminal: echo "Feature.enable(:compliance_violations_report)" | rails c
3. View the compliance report and verify that the filter syncs with the URL query: [GDK_HOST]/groups/gitlab-org/-/security/compliance_dashboard

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 #342897 (closed)