Add basic YAML test_harness tests

Works, however ignores a lot of fields in the YAML.

beacon_node/beacon_chain/test_harness/examples/chain.yaml

@@ -0,0 +1,77 @@
+title: Sample Ethereum Serenity State Transition Tests
+summary: Testing full state transition block processing
+test_suite: prysm
+fork: sapphire
+version: 1.0
+test_cases:
+  - config:
+      epoch_length: 64
+      deposits_for_chain_start: 1000
+      num_slots: 32 # Testing advancing state to slot < SlotsPerEpoch
+    results:
+      slot: 32
+      num_validators: 1000
+  - config:
+      epoch_length: 64
+      deposits_for_chain_start: 16384
+      num_slots: 64
+      deposits:
+        - slot: 1
+          amount: 32
+          merkle_index: 0
+          pubkey: !!binary |
+            SlAAbShSkUg7PLiPHZI/rTS1uAvKiieOrifPN6Moso0=
+        - slot: 15
+          amount: 32
+          merkle_index: 1
+          pubkey: !!binary |
+            Oklajsjdkaklsdlkajsdjlajslkdjlkasjlkdjlajdsd
+        - slot: 55
+          amount: 32
+          merkle_index: 2
+          pubkey: !!binary |
+            LkmqmqoodLKAslkjdkajsdljasdkajlksjdasldjasdd
+      proposer_slashings:
+        - slot: 16 # At slot 16, we trigger a proposal slashing occurring
+          proposer_index: 16385 # We penalize the proposer that was just added from slot 15
+          proposal_1_shard: 0
+          proposal_1_slot: 15
+          proposal_1_root: !!binary |
+            LkmqmqoodLKAslkjdkajsdljasdkajlksjdasldjasdd
+          proposal_2_shard: 0
+          proposal_2_slot: 15
+          proposal_2_root: !!binary |
+            LkmqmqoodLKAslkjdkajsdljasdkajlksjdasldjasdd
+      attester_slashings:
+        - slot: 59 # At slot 59, we trigger a attester slashing
+          slashable_vote_data_1_slot: 55
+          slashable_vote_data_2_slot: 55
+          slashable_vote_data_1_justified_slot: 0
+          slashable_vote_data_2_justified_slot: 1
+          slashable_vote_data_1_custody_0_indices: [16386]
+          slashable_vote_data_1_custody_1_indices: []
+          slashable_vote_data_2_custody_0_indices: []
+          slashable_vote_data_2_custody_1_indices: [16386]
+    results:
+      slot: 64
+      num_validators: 16387
+      penalized_validators: [16385, 16386] # We test that the validators at indices 16385, 16386 were indeed penalized
+  - config:
+      skip_slots: [10, 20]
+      epoch_length: 64
+      deposits_for_chain_start: 1000
+      num_slots: 128 # Testing advancing state's slot == 2*SlotsPerEpoch
+      deposits:
+        - slot: 10
+          amount: 32
+          merkle_index: 0
+          pubkey: !!binary |
+            SlAAbShSkUg7PLiPHZI/rTS1uAvKiieOrifPN6Moso0=
+        - slot: 20
+          amount: 32
+          merkle_index: 1
+          pubkey: !!binary |
+            Oklajsjdkaklsdlkajsdjlajslkdjlkasjlkdjlajdsd
+    results:
+      slot: 128
+      num_validators: 1000 # Validator registry should not have grown if slots 10 and 20 were skipped