Add integration and unit tests for mempool.space websocket client, API and fns

[oleonardolima]

Description:

Using the bitcoind and mempool/backend we need to implement some integration and unit tests for the client build in #3. When generating blocks, it should be consumed and returned as a stream of BlockEvents.

Resources:

• bitcoind: https://github.com/RCasatta/bitcoind
• mempool: https://github.com/mempool/mempool/
• testcontainers: https://github.com/testcontainers/testcontainers-rs