Further test the Carrier

[sr-gi]

The Carrier is the main interface between the tower and bitcoind.

Currently, several possible errors are taken into account, however, many more may not have a specific covered case. This needs further testing.

This requires https://github.com/talaia-labs/rust-teos/issues/34 being landed. Cannot be tested with a simple mock.

Checking https://github.com/talaia-labs/rust-teos/issues/35 is highly encouraged here.