feat(wallet-integration): server and API (#362)

* feat(wallet-integration): implement server and API

* feat(wallet-integration): add a few tests to server. Needs more

* refactor(wallet-integration): just use call_data, remove data types

* feat(wallet-integration): add frontend type for flexible serving

* feat(wallet-integration): StateHandler in WalletIntegrationManager. Add terminate method

* refactor(wallet-integration): move to module with pop-cli crate

* feat(wallet-integration): server-side error handling, update port to 9090

* refactor(wallet-integration): restructure server for easier use in thread

* fix(wallet-integration): remove invalid fn `finish`

* docs(wallet-integration): inline comments

* test(wallet-integration): unit tests for wallet-integration server. Add new frontend type

* feat(wallet-integration): two new routes: error and terminate

* refactor(wallet-integration): consistent comments, remove unnecessary code in tests

* feat: add TransactionData::new

* refactor(wallet-integration: shutdown channel error handling, terminate helper, take_error and TranscationData::new tests

* chore: clippy warning