Extract should_replace from Scoring and supply pooled txs from same sender

[ascjones]

should_replace does not use the computed score, and is actually called only on import (when pool limits are reached).

Further, we pass other pooled transactions from the respective senders of the old and new transactions which are being compared. This would allow an implementation to also compare the Readiness of the transactions when deciding if the new should push out the old.

[tomusdrw]

lgtm! We should bump the version of the crate though.

[ascjones]

Bump to version 2.0?

[tomusdrw]

Seems like there is still an issue with tests:

error[E0053]: method `should_replace` has an incompatible type for trait
  --> transaction-pool/src/tests/helpers.rs:77:20
   |
77 |     fn should_replace(&mut self, old: &ReplaceTransaction<Transaction>, new: &ReplaceTransaction<Transaction>) -> scoring::Choice {
   |                       ^^^^^^^^^ types differ in mutability
   | 
  ::: transaction-pool/src/replace.rs:52:23
   |
52 |     fn should_replace(&self, old: &ReplaceTransaction<T>, new: &ReplaceTransaction<T>) -> Choice;
   |                       ----- type in trait
   |
   = note: expected type `fn(&tests::helpers::DummyScoring, &replace::ReplaceTransaction<'_, tests::Transaction>, &replace::ReplaceTransaction<'_, tests::Transaction>) -> scoring::Choice`
              found type `fn(&mut tests::helpers::DummyScoring, &replace::ReplaceTransaction<'_, tests::Transaction>, &replace::ReplaceTransaction<'_, tests::Transaction>) -> scoring::Choice`
help: consider change the type to match the mutability in trait
   |
77 |     fn should_replace(&self, old: &ReplaceTransaction<Transaction>, new: &ReplaceTransaction<Transaction>) -> scoring::Choice {
   |                       ^^^^^

[tomusdrw]

Merging since appveyor failures are unrelated and travis only failed the windows build (due to timeout).