Prevent send to token

[estebanmino]

This PR prevents users to send tokens to contract addresses in eth-contract-metadata or tokens added manually.

GIF to show the UX

The first address is "HACK" address, the second one is one from eth-contract-metadata.

Fixes #3185

[metamaskbot]

Builds ready [6dd7b69]: mascara, chrome, firefox, edge, opera

[metamaskbot]

Builds ready [ce2d48a]: mascara, chrome, firefox, edge, opera

[danfinlay]

This is a great user protection, thank you!

[JiimyZee]

When were any of these "known contract warnings" actually implemented because I can see you all have been working on this since 2016?

[github-actions]

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[JiimyZee]

CLA Signature Action:

Thank you for your submission, we really appreciate it. We ask that you read and sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just by adding a comment to this pull request with this exact sentence:

I have read the CLA Document and I hereby sign the CLA

By commenting with the above message you are agreeing to the terms of the CLA. Your account will be recorded as agreeing to our CLA so you don't need to sign it again for future contributions to this repository.

0 out of 1 committers have signed the CLA. ❌ @estebanmino

I have read the CLA Document and I hereby sign the CLA