(trivial) wallet: rename parameter of a method

Re get_change_addresses_for_new_transaction,
"allow_reuse" is a confusing parameter name:
it means whether we allow reusing already used change addresses to send new change to.
However, if the method returns [], we will instead reuse the "from address" and send change there.
So it quite unclear without thinking it through what "allow_reuse" means as it could be either
of the two (and they are ~opposite scenarios).
The new name is long but at least it is clear.

electrum/wallet.py

@@ -1258,7 +1258,7 @@ class Abstract_Wallet(AddressSynchronizer, ABC):
         return candidate
 
     def get_change_addresses_for_new_transaction(
-            self, preferred_change_addr=None, *, allow_reuse: bool = True,
+            self, preferred_change_addr=None, *, allow_reusing_used_change_addrs: bool = True,
     ) -> List[str]:
         change_addrs = []
         if preferred_change_addr:
@@ -1276,7 +1276,7 @@ class Abstract_Wallet(AddressSynchronizer, ABC):
                 change_addrs = addrs
             else:
                 # if there are none, take one randomly from the last few
-                if not allow_reuse:
+                if not allow_reusing_used_change_addrs:
                     return []
                 addrs = self.get_change_addresses(slice_start=-self.gap_limit_for_change)
                 change_addrs = [random.choice(addrs)] if addrs else []
@@ -1289,11 +1289,11 @@ class Abstract_Wallet(AddressSynchronizer, ABC):
         return change_addrs[:max_change]
 
     def get_single_change_address_for_new_transaction(
-            self, preferred_change_addr=None, *, allow_reuse: bool = True,
+            self, preferred_change_addr=None, *, allow_reusing_used_change_addrs: bool = True,
     ) -> Optional[str]:
         addrs = self.get_change_addresses_for_new_transaction(
             preferred_change_addr=preferred_change_addr,
-            allow_reuse=allow_reuse,
+            allow_reusing_used_change_addrs=allow_reusing_used_change_addrs,
         )
         if addrs:
             return addrs[0]
@@ -1801,7 +1801,7 @@ class Abstract_Wallet(AddressSynchronizer, ABC):
         if not item:
             raise CannotCPFP(_("Could not find coins for output"))
         inputs = [item]
-        out_address = (self.get_single_change_address_for_new_transaction(allow_reuse=False)
+        out_address = (self.get_single_change_address_for_new_transaction(allow_reusing_used_change_addrs=False)
                        or self.get_unused_address()
                        or address)
         output_value = value - fee