Migrate nonce-tracking from `web3-provider-engine` to transaction controller

[Gudahtt]

The transaction controller currently relies on the nonce-tracker middleware in web3-provider-engine to ensure that the suggested nonce used is greater than any pending transactions.

We should switch to using the nonce-tracker library for this purpose instead, like the extension does.

[xinnanyemm]

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[Gudahtt]

It looks like getting a proxied provider and block tracker are a practical necessity for using the nonce tracker correctly, because we can't destroy it and recreate it each network switch without getting into tricky lock situations. I'll have to mark this as blocked by #1018

[Gudahtt]

This issue requires the addition of middleware on metamask-mobile to ensure that there is no impact to the dapp API, because the nonce tracker middleware in web3-provider-engine being replaced also has a dapp-facing impact. The impact is that the eth_getTransactionCount will include pending transactions in the count returned if you ask for the pending block.

This feature has been implemented on mobile in this branch: https://github.com/MetaMask/metamask-mobile/tree/refactor-get-transaction-count

It needs to be rebased and it needs to be tested, but otherwise it's just blocked by this transaction controller work.

[adonesky1]

We're not aiming to add a pendingTransactionsController as well are we? Its not clear to me how this functionality is mirrored on the core side

[Gudahtt]

I don't think that would be necessary. That class handles checking the status of pending transactions, which is already done directly in the core transaction controller.