Add standards adherence tab to compliance report

What does this MR do and why?

What

• Adds a new feature flag :adherence_report_ui
• Adds new tab on the compliance report page
• Adds base component for new adherence report
• Updates router based on feature flag

Why

Part of Phase 1 as outlined in #413558 (closed)

Screenshots or screen recordings

feature :adherence_report_ui disabled	feature :adherence_report_ui enabled

How to set up and validate locally

1. Visit a group, under Secure (new UI) or Security & Compliance (old UI) > Compliance report
2. Observe no new tab
3. In the rails console (rails c) enable feature (Feature.enable(:adherence_report_ui))
4. Visit a group, under Secure (new UI) or Security & Compliance (old UI) > Compliance report
5. Observe new tab

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 #413716 (closed)