New API changes

[gabaldon]

This PR uses the new explorer api v1.5 with the latest witnet.dart changes:

• Updates gem file and pod file to support Xcode 15
• Implements ValueTransferInfo adapters for compatibility with DB
• Stops using witnet.dart adapters to store values in DB
• Supports new ValueTransferInfo schema and allow migrating DB
• Deletes unused methods in api_explorer
• Updates use of explorer api results as now pagination is supported
• Uses TxStatusLabel enum instead of string
• Updates sendTransaction result as now it returns a string instead of a boolean
• UpdatesInputUtxo and use new outputPointer.toString() witnet.dart method to compare UTXOS

This PR depends on https://github.com/witnet/witnet.dart/pull/49 and https://github.com/witnet/witnet.dart/pull/54 close #446 close https://github.com/witnet/witnet.dart/issues/51 close https://github.com/witnet/my-wit-wallet/issues/504