Add modal to Buy storage button

What does this MR do and why?

Add a modal window with information for customers that have limitations to buy storage. Currently feature is behind limited_access_modal FF.

Criteria to show the modal:

• limited_access_modal FF is ON
• ramp or reseller subscription (in this case API returns canAddSeats: false. We rely on this field even though we add not seats but storage here

We have this modal already implemented for Add seats button !131533 (merged)

Related to #409750 (closed)

Screenshots or screen recordings

Buy Storage on a standard card	Buy storage on Excess Breakdown card
Screen_Recording_2023-09-20_at_16.12.25	Screen_Recording_2023-09-20_at_14.05.12

How to set up and validate locally

• Create a ramp subscription
• Create a reseller subscription
• Create a subscription without either reseller or ramp attributes
• Run rails c and then `Feature.enable(:limited_access_modal)

For both ramp + reseller subscriptions:

• Link it to a GL namespace either in the CDot UI (subscriptions/SUBSCRIPTION_NAME/edit?transaction=change_gitlab_group) or via the rails console
• In GL, navigate to /groups/GROUP_NAME/-/usage_quotas#storage-quota-tab
• Verify that Buy storage button appears as usual
• Verify that clicking the button displays the modal and it has a different text for RAMP and RESELLER
• Verify that closing out of the modal functions properly

For old flow - hardcode isUsingProjectEnforcement: false in ee/app/assets/javascripts/usage_quotas/storage/init_namespace_storage.js#L46

For the regular subscription:

• Link it to a GL namespace either in the CDot UI (subscriptions/SUBSCRIPTION_NAME/edit?transaction=change_gitlab_group) or via the rails console
• In GL, navigate to /groups/GROUP_NAME/-/usage_quotas#storage-quota-tab
• Verify that Buy storage button appears as usual
• Verify that clicking the button takes you to CDot to add seats

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.