Add unit tests for optimizer for orders with more than 2 different base tokens

[DanilYachmenev]

Add unit tests for DaoCross optimizer in defi/tulip/test/test_optimize.py

• Create orders with 4 different base tokens
  • 4 orders for each token
  • 1 buy order with the limit price cond = True
  • 1 buy order with the limit price cond = False
  • 2 sell orders with the same logic
• Use TestRunSolver3 as reference

  ...
  _actions = ["buy", "buy", "sell", "sell", ...
  _quantities = [4, 2, 5, 3 ...
  _base_tokens = ["BTC", ..., "ETH", ..., "ADA", ..., "DOGE", ...]
  _quote_tokens = ["ETH", ..., "DOGE", ..., "BTC", ..., "ADA", ...]

• Replace TestRunSolver4 with this test

  # TODO(Grisha): replace with the class that tests for N random orders.
  # TODO(Grisha): use `_generate_test_orders()` to get the orders.
  class TestRunSolver4(hunitest.TestCase):

@samarth9008, @okritvik to distribute FYI @gpsaggese

[DanilYachmenev]

@lokashrinav how's it going with the task? have any questions?