Remove 2p payjoin support

Payjoin support is mostly adding boiler plate and getting
in the way of multiparty work. At this point its unlikely we will learn anything
new from supporting payjoin -- both interms of the cost function and tx structure.

Author: arminsabouri

config.toml.example

@@ -4,10 +4,10 @@ max_timestep = 10
 num_payment_obligations = 15
 
 [[wallet_types]]
-name = "Payjoiner"
+name = "default"
 count = 3
 script_type = "p2tr"
-strategies = ["UnilateralSpender", "PayjoinStrategy"]
+strategies = ["UnilateralSpender", "BatchSpender"]
 [wallet_types.scorer]
 fee_savings_weight = 1.0
 privacy_weight = 2.0