Select RPC URL - Add back button to be able go back to the Select a Network page

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### What is this about?

Whenever I click Select RPC URL, I land into the new modal page for selecting the RPC URL. Once I reach this point, I can only select the RPC or close.
It would be very convenient to have an arrow button on top, to go back to the Select Network modal page

See no possibility to go back:


See example on Edit Network, where we do have the possibility to go back clicking the arrow:


### Scenario

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### Design

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### Technical Details

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### Threat Modeling Framework

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### Acceptance Criteria

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### 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
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### References

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Start by tracing the Select Network modal into the Select RPC URL modal in the MetaMask extension UI. Compare that flow with the existing back-arrow behavior on Edit Network. Done means the Select RPC URL view has a back control that returns to Select Network without closing the modal.

Written by the indexing model from the issue text.