Update Registration Features CTA for repository size limit

What does this MR do and why?

Related to #349307 (closed)

We need to update the method to show the Registration Features CTA implemented at !73222 (merged). This requires:

• Adding CE templates with only the CTA (one for groups and projects settings, and one for application settings)
• Adding content-based tests for the CTA behavior.
• Using the new registration_features_can_be_prompted helper.

Criteria to show the CTA

The offer shouldn't be presented to licensed instances because they already have the paid features available, so the callout (to enable features they already have) doesn't make sense. The decision on whether to show the offer is on the true/false of whether Service Ping is enabled, not on whether Registration Features is enabled.

Instance Type	License Type	Service Ping Setting	Expected Behavior
CE	Unlicensed	Off	Link to docs
EE	Unlicensed	Off	Link to admin setting
EE	Licensed	Off	Do not present offer
CE	Unlicensed	On	Do not present offer
EE	Unlicensed	On	Do not present offer
EE	Licensed	On	Do not present offer

Screenshots or screen recordings

This MR doesn't introduce visual changes. The following is meant as context. 🙇

The following screenshots are from the group's settings page.

Enabled feature for reference

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When Service Ping is disabled

The CTA is always hidden if Service Ping is enabled.

Before (hidden)	After (CE)	After (EE)

How to set up and validate locally

1. Go to the corresponding section for setting the size limit for groups, projects, or global.
2. Scroll to the Size limit per repository (MB) or Repository size limit (MB) field.
3. Toggle a local license/subscription and/or service ping/registration features.

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.