Add product analytics usage table for projects

What does this MR do and why?

Adds a table to the new usage quota page showing the usage of each project within the group.

Each project will show usage for the previous and current month.

This MR is part of a series to build the new product analytics usage quota page:

Merge request	status
create app structure	✔
projects usage table	<-- you are here
projects usage visualization	⌛
projects usage visualization	⌛
total group usage visualization	⌛
feature flag rollout	⌛

Screenshots or screen recordings

Before	After
(feature flag enabled, product analytics available)
	(no product analytics projects in group for current period (to be improved))
	(product analytics onboarded projects found, but no events)
	(error fetching projects usage data)
	(loading state)
(feature flag disabled or product analytics unavailable)	(unchanged)

How to set up and validate locally

1. Requires GitLab Ultimate.

2. Follow these instructions to set up Product Analytics in your GDK.

3. Enable product analytics

4. Enable product_analytics_usage_quota feature flag

5. Visit a group -> Settings -> Usage Quota (verify empty state)

6. Onboard a project with product analytics

7. Verify table displays with expected data

To verify the error state, visit the usage quota page and then disable the network within devtools before clicking the product analytics 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 #424152 (closed)