Add beacon.watch (#3362)

> This is currently a WIP and all features are subject to alteration or removal at any time.

## Overview

The successor to #2873.

Contains the backbone of `beacon.watch` including syncing code, the initial API, and several core database tables.

See `watch/README.md` for more information, requirements and usage.

watch/src/database/schema.rs

@@ -0,0 +1,102 @@
+// @generated automatically by Diesel CLI.
+
+diesel::table! {
+    active_config (id) {
+        id -> Int4,
+        config_name -> Text,
+        slots_per_epoch -> Int4,
+    }
+}
+
+diesel::table! {
+    beacon_blocks (slot) {
+        slot -> Int4,
+        root -> Bytea,
+        parent_root -> Bytea,
+        attestation_count -> Int4,
+        transaction_count -> Nullable<Int4>,
+        withdrawal_count -> Nullable<Int4>,
+    }
+}
+
+diesel::table! {
+    block_packing (slot) {
+        slot -> Int4,
+        available -> Int4,
+        included -> Int4,
+        prior_skip_slots -> Int4,
+    }
+}
+
+diesel::table! {
+    block_rewards (slot) {
+        slot -> Int4,
+        total -> Int4,
+        attestation_reward -> Int4,
+        sync_committee_reward -> Int4,
+    }
+}
+
+diesel::table! {
+    blockprint (slot) {
+        slot -> Int4,
+        best_guess -> Text,
+    }
+}
+
+diesel::table! {
+    canonical_slots (slot) {
+        slot -> Int4,
+        root -> Bytea,
+        skipped -> Bool,
+        beacon_block -> Nullable<Bytea>,
+    }
+}
+
+diesel::table! {
+    proposer_info (slot) {
+        slot -> Int4,
+        proposer_index -> Int4,
+        graffiti -> Text,
+    }
+}
+
+diesel::table! {
+    suboptimal_attestations (epoch_start_slot, index) {
+        epoch_start_slot -> Int4,
+        index -> Int4,
+        source -> Bool,
+        head -> Bool,
+        target -> Bool,
+    }
+}
+
+diesel::table! {
+    validators (index) {
+        index -> Int4,
+        public_key -> Bytea,
+        status -> Text,
+        activation_epoch -> Nullable<Int4>,
+        exit_epoch -> Nullable<Int4>,
+    }
+}
+
+diesel::joinable!(block_packing -> beacon_blocks (slot));
+diesel::joinable!(block_rewards -> beacon_blocks (slot));
+diesel::joinable!(blockprint -> beacon_blocks (slot));
+diesel::joinable!(proposer_info -> beacon_blocks (slot));
+diesel::joinable!(proposer_info -> validators (proposer_index));
+diesel::joinable!(suboptimal_attestations -> canonical_slots (epoch_start_slot));
+diesel::joinable!(suboptimal_attestations -> validators (index));
+
+diesel::allow_tables_to_appear_in_same_query!(
+    active_config,
+    beacon_blocks,
+    block_packing,
+    block_rewards,
+    blockprint,
+    canonical_slots,
+    proposer_info,
+    suboptimal_attestations,
+    validators,
+);