Consolidate test doubles

- Migrate various mocks of core namespaces to shared version in `fakes` pkg
- Err on the side of making test doubles less sophisticated
- Don't pull over mocks of namespaces that are only used in example code

pkg/geth/client/eth_client.go

@@ -0,0 +1,42 @@
+package client
+
+import (
+	"context"
+	"github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethclient"
+	"math/big"
+)
+
+type EthClient struct {
+	client *ethclient.Client
+}
+
+func NewEthClient(client *ethclient.Client) EthClient {
+	return EthClient{client: client}
+}
+
+func (client EthClient) BlockByNumber(ctx context.Context, number *big.Int) (*types.Block, error) {
+	return client.client.BlockByNumber(ctx, number)
+}
+
+func (client EthClient) CallContract(ctx context.Context, msg ethereum.CallMsg, blockNumber *big.Int) ([]byte, error) {
+	return client.client.CallContract(ctx, msg, blockNumber)
+}
+
+func (client EthClient) FilterLogs(ctx context.Context, q ethereum.FilterQuery) ([]types.Log, error) {
+	return client.client.FilterLogs(ctx, q)
+}
+
+func (client EthClient) HeaderByNumber(ctx context.Context, number *big.Int) (*types.Header, error) {
+	return client.client.HeaderByNumber(ctx, number)
+}
+
+func (client EthClient) TransactionSender(ctx context.Context, tx *types.Transaction, block common.Hash, index uint) (common.Address, error) {
+	return client.client.TransactionSender(ctx, tx, block, index)
+}
+
+func (client EthClient) TransactionReceipt(ctx context.Context, txHash common.Hash) (*types.Receipt, error) {
+	return client.client.TransactionReceipt(ctx, txHash)
+}