Mainly refactor API to have control on pending_transactions operations.
Use the new API to migrate the multi-transaction ID from to transfers
in one SQL transaction.
The refactoring was done to better mirror the purpose of pending_transactions
Also:
- Externalize TransactionManager from WalletService to be used by
other services
- Extract walletEvent as a dependency for all services that need to
propagate events
- Batch chain requests
- Remove unused APIs
- Add auto delete option for clients that fire and forget transactions
Updates status-desktop #11754
Stefan