Export last activity details - seat usage quotas page

What does this MR do and why?

Related Issue: #362751 (closed)

This MR adds additional attributes (last_active_at, last_sign_in_at) to the exported CSV file in the seat usage quotas page.

Screenshots or screen recordings

Before:

After:

How to set up and validate locally

1. Checkout the feature branch
2. Navigate to any group's usage quotas page(example: http://localhost:3000/groups/twitter/-/usage_quotas#seats-quota-tab)
3. Select the Export list option and review the downloaded csv file - includes additional attributes (last_active_at, last_sign_in_at)

MR acceptance checklist

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