Add status check drawer component to branch rule setting page

What does this MR do and why?

Adds a placeholder drawer to add/edit status check in the branch rules page. As of this MR, add, edit or delete is not functioning.

Part 1 of Issue: #439396 (closed)

⚠ Note: changes in this MR are behind the :edit_branch_rules feature flag.

Implementation breakdown:

Description	Issue/MR
Add status checks drawer placeholder component	👈 This MR
Add status check in drawer	follow-up MR
Edit status check in drawer	follow-up MR
Update doc	follow-up MR

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After (flag ON)	After (flag OFF)
	Screen_Recording_2024-07-30_at_1.19.49_PM

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Enable the edit-branch-rules feature flag
2. Add a Branch rule
   • Navigate to Project > Repository > Settings > Branch rules > Add branch rule
3. View the branch rule created in step 1
   • Navigate to Project > Repository > Settings > Branch rules > View details
4. On the Branch rule details screen, existing status checks should display properly
5. Select add status check should open a drawer with service name and api fields

Related to #439401 (closed)