Do not require .eth when typing ENS domain address when connected to Ethereum mainnet

### What is this about?

I would assume that when using Metamask connected to Ethereum network the ENS is the default?

I was perplexed that I need to explicitly type `.ens` as if there were multiple competitors and using a smart default was bad.

And then some commentary / rant: https://www.youtube.com/watch?v=KhOd1oSSwdg

1. Confused about conversion, didn't see that feature, not sure why is there, seems advanced to me, should be hidden
2. No character count when typing a message
3. No button back to blue when deleting
4. Clicking on link closes the popup and loses progress
5. Link does not work anyway (at this point it didn't surprise me, it just proved the point 🤯)

FYI: I use irony and sarcasm in the video. Tone of voice to get some likes / clicks / nothing personal.

### Scenario

N/A

### Design

N/A

### Technical Details

N/A

### Threat Modeling Framework

N/A

### Acceptance Criteria

N/A

### 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

N/A

No files, tests, entry points, or acceptance criteria are identified in the issue. First clarify the expected ENS resolution behavior on Ethereum mainnet, then locate the address-entry flow and add coverage showing that a domain without an explicit suffix resolves correctly; done means the mainnet flow no longer requires the suffix.

Written by the indexing model from the issue text.