Shareable request link needs copy improvements

### What is this about?

As a user, if I'm choosing the CTA `Send Link`, there should be some auto-filled suggested copy for the SMS message being sent. As it appears now, it is just a link with no context and looks very scammy. Even something like "Here's a link to how you can pay me on MetaMask..." would be a nice starter!

Also could rewrite the copy in the URL to be more descriptive than metamask.app.link.

### Scenario

_No response_

### Design

https://github.com/user-attachments/assets/9186ce00-1e85-4f0a-aa03-fb865cec2fcf

### Technical Details

_No response_

### Threat Modeling Framework

_No response_

### Acceptance Criteria

_No response_

### Stakeholder review needed before the work gets merged

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References

_No response_