[Mega tracking] - Implement policing service

[shayzluf]

While starting the design process of policing service that will keep an eye at the network for finding slashable events. as well as protect his own subscribers (Validators) from creating a slashable event.

The way to a full blown policing service is comprised of these steps:
Bug fixes:

• grpc proto api watchtower api #3134

• separate db for slasher Slasher db #3270

• making slasher grpc server Slasher grpc service #3271

• Store historical block headers in local db Slasher db #3270

• Store indexed attestations in db Indexed attestations store #3322 / Fix indexed attestations Slasher store #3897

• Store min max span per validator Store Validators Min and Max Spans for Slashing #3941

• Update min max span per validator min max span update logic #3951

• Detect surround attestations using min max span Surround detection #3967

• Proposer slashing detection (db keys)

• Double Attestation detection (db keys)

• Surround attestation detection (min max span)

• Benchmark surround attestation detection

• Slasher grpc client of beacon node

• Store active validator state per epoch

• Store validator index to public key map

• Validate attestation signature (@rauljordan @0xKiwi they are verified before being put in pull)

• Purge attestations and historic block headers bucket to max size Slasher db #3270

• Beacon server detection of all slashable events of its subscribed validators(bitmap 54000 epoches X number of running validators). By storing all the data concerning them in db and validating against it. Panic in case a rpc call is going to create a slashable event.

• Slasher server with pruning at weak subjectivity period

• Beacon node / Slasher communication. to feed slasher with attestations and block proposals.

• Beacon node / Slasher communication. to listen slashable events

• Slashing simulator

[prestonvanloon]

Design doc: https://docs.google.com/document/d/12Eg-ysK5aQKQIjTKL6srqu8-ZY44iZ2MNwuqPaymlYk/edit#

[rauljordan]

Suggestion to name the watchtower server Bazel binary that's in charge of policing slashable events across beacon nodes the "Hash Slinging Slasher" after the iconic Spongebob Squarepants villain (credits to @prestonvanloon)

[shayzluf]

Suggestion to name the watchtower server Bazel binary that's in charge of policing slashable events across beacon nodes the "Hash Slinging Slasher" after the iconic Spongebob Squarepants villain (credits to @prestonvanloon)

should i change the folder name?

[rauljordan]

Closing this in favor of #4836