Reset profit counters at start of each sim run

[chanhosuh]

Set virtual price, xcp profit (regular and admin), to 10**18 in prepare_for_run.

[nagakingg]

Proposed: insert the second code block into SimCurveCryptoPool.prepare_for_run()

Note: this will change the SimCurveCryptoPool end-to-end test results

    def prepare_for_run(self, prices):
        xcp = self._get_xcp(self.D)
        n = self.n

        if n == 2:
            root = _sqrt_int
        elif n == 3:
            root = _cbrt

        # Get/set initial prices
        initial_prices = prices.iloc[0, 0 : n - 1].tolist()
        initial_prices = [int(10**18 / p) for p in initial_prices]

        self.last_prices = initial_prices
        self.price_scale = initial_prices
        self._price_oracle = initial_prices

        # Set virtual price & xcp profit to 1
        self.tokens = xcp
        self.xcp_profit = 10**18
        self.xcp_profit_a = 10**18

        # Upbdate balances, preserving xcp
        initial_prices_root = [root(p) for p in initial_prices]
        new_D = prod(initial_prices_root) * xcp * n // 10 ** (18 * (n - 1))
        balances = self._convert_D_to_balances(new_D)
        self.balances = balances

        # Recompute and store D & virtual_price
        xp = self._xp()  # pylint: disable=protected-access
        computed_D = newton_D(self.A, self.gamma, xp)
        self.D = computed_D

        virtual_price = self.get_virtual_price()
        self.virtual_price = virtual_price