Guide on using Flashbots Protect RPC on Admin for private transactions

[spalladino]

We've received requests for sending private txs (ie txs not visible on the mempool, so they cannot be frontrun) via Admin (also via Relayer, but that's a different story). Since txs in Admin are sent from the user's wallet, this can be done just by configuring the Flashbots Protect RPC endpoint on Metamask as described here.

Write a short guide explaining why private txs are useful, linking to Flashbots Protect guide on metamask setup, and showing an example of executing a multisig action using the Protect endpoint.