FRP: FHE and MEV

[mlvl36667]

This PR adds a Flashbots Research Proposal on the use of Fully Homomorphic Encryption in MEV-related settings.

[sarahalle]

Thanks for submitting this proposal! We aren't moving forward to support the project for two reasons:

1. The data set you propose to collect is already maintained for other MEV research projects.
2. The model used for FHE application deviates from what we would expect in terms of which parties could act on the encrypted information. Without a specific implementation to research, it is hard to ensure the findings could apply to future practice.