feat: test suits for new stateful tests

* adds an initial test suit that only swaps a seeded pool.

* placeholder for all the future test cases was added

tests/unitary/pool/stateful/test_stateful2.py

@@ -0,0 +1,77 @@
+import boa
+from hypothesis import note
+from hypothesis.stateful import rule
+from hypothesis.strategies import data, integers, just
+from stateful_base2 import StatefulBase
+
+
+class OnlySwapStateful(StatefulBase):
+    """This test suits always starts with a seeded pool
+    with balanced amounts and execute only swaps depending
+    on the liquidity in the pool.
+    """
+
+    @rule(
+        data=data(),
+        i=integers(min_value=0, max_value=1),
+        user=just(boa.env.generate_address()),
+    )
+    def exchange(self, data, i: int, user: str):
+        liquidity = self.coins[i].balanceOf(self.pool.address)
+        dx = data.draw(
+            integers(
+                min_value=int(liquidity * 0.0001),
+                max_value=int(liquidity * 0.85),
+            ),
+            label="dx",
+        )
+        note("trying to swap: {:.3%} of pool liquidity".format(dx / liquidity))
+        return super().exchange(dx, i, user)
+
+
+class UpOnlyLiquidityStateful(OnlySwapStateful):
+    """This test suite does everything as the OnlySwapStateful
+    but also adds liquidity to the pool. It does not remove liquidity."""
+
+    # TODO
+    pass
+
+
+class OnlyBalancedLiquidityStateful(UpOnlyLiquidityStateful):
+    """This test suite does everything as the UpOnlyLiquidityStateful
+    but also removes liquidity from the pool. Both deposits and withdrawals
+    are balanced.
+    """
+
+    # TODO
+    pass
+
+
+class UnbalancedLiquidityStateful(OnlyBalancedLiquidityStateful):
+    """This test suite does everything as the OnlyBalancedLiquidityStateful
+    but also removes liquidity from the pool. Deposits and withdrawals can
+    be unbalanced.
+
+    This is the most complex test suite and should be used when making sure
+    that some specific gamma and A can be used without unexpected behavior.
+    """
+
+    # TODO
+    pass
+
+
+class RampingStateful(UnbalancedLiquidityStateful):
+    """This test suite does everything as the UnbalancedLiquidityStateful
+    but also ramps the pool. Because of this some of the invariant checks
+    are disabled (loss is expected).
+    """
+
+    # TODO
+    pass
+
+
+TestOnlySwap = OnlySwapStateful.TestCase
+# TestUpOnlyLiquidity = UpOnlyLiquidityStateful.TestCase
+# TestOnlyBalancedLiquidity = OnlyBalancedLiquidityStateful.TestCase
+# TestUnbalancedLiquidity = UnbalancedLiquidityStateful.TestCase
+# RampingStateful = RampingStateful.TestCase