* Wallet prep work for BPU
This PR prepares the wallet for #1321. It makes transfers from the vault and ledger to go to their own post actions for processing (not particularly useful in this PR but is needed in BPU to propose a new tx) It also makes the Sign with seed consistent with redirect to /psbt/ready after signing which it did not do (it stayed on the seed route)
* fix test
* add assert
* BitcoinSpecificBtcPayNetwork - abstract BTCPayNetwork
* some type fixes
* fix tests
* simplify fetching handler in invoice controller
* rename network base and bitcoin classes
* abstract serializer to network level
* fix serializer when network not provided
* fix serializer when network not provided
* fix serializer when network not provided
* try fixes for isolating pull request
* Make wallet able to send to multiple destinations
* fix tests
* update e2e tests
* fix e2e part 2
* make headless again
* pr changes
* make wallet look exactly as old one when only 1 dest
