feat: add lock target

[marktoda]

This commit adds a lockTarget parameter to lock where any caller can specify a locker to handle the routing logic on their behalf. This can allow safe storage via tstore and passing usage of the lock initiator to hook callbacks

closes #298

Related Issue

Which issue does this pull request resolve?

Description of changes

[marktoda]

[WIP] needs tests

[marktoda]

if we do this, future TODO is to tstore the actual msg.sender and pass it as a param to hook calls

[marktoda]

Seemingly pretty serious gas improvements:

simple swap: 203264 simple swap EOA initiated: 174949 simple swap native: 191605 simple swap EOA initiated native: 168498

[ewilz]

are gas savings the only reason for this PR? bc I imagine we'll inevitably go through the router anyway since we tend to aggregate across versions, so I imagine this will actually be a gas increase overall for our app? UNless we want to special case v4-only swaps and save for that subset of swaps... But for aggregators etc, gas goes up