Describe the usability problem
We upgraded the core Send flow, but we still trigger old Send UI in certain cases. This makes for a inconsistent feel of the product for users.

1. When a payment request link is opened. The old Send confirmation screen pops up
   

2. On Confirm transaction screen, 'Edit' takes user to old Send screen (when triggered from deeplink and within app)
   

3. Deeplinks https://metamask.github.io/metamask-deeplinks/

Payment requests for ETH (same link as payment request link generated from within MetaMask 'Request' feature triggers this Old Send screen):

Payment requests for an ERC20 token (same link as payment request link generated from within MetaMask 'Request' feature triggers this Old Send screen):

Payment Channel request opens a different UI then old Send confirm. Adding here as this is inconsistent as well.

Expected behavior
If possible, a clear and concise description / resolution of what you expected to happen

Payment request case

1. When a user taps on a ETH or ERC20 payment request link, New Send confirmation screen should be triggered with recipient address, asset type, amount pre-filled.

2. User can edit any of these fields (from, to, amount, asset, fee) similar to how they can edit them in the new send flow. Maybe a slight difference than New Send flow edit behavior would be possibility to change 'from' from the Send confirmation screen.

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