feat: add tests for receiving funds

[limpbrains]

Depends on #84

• tests for receiving funds
• emit "transactionReceived" event later, when the wallet state might be more accurate
• new MessageListener class to test wallet onMessage

I also moved before / beforeEach methonds inside describe to avoid executing them before all tests. They were interfearing and breaking electrum connection.

Before

Storage before
Transaction before
Wallet before
  Boost
Boost beforeEach
    ✔ Should fail in some cases. (2664ms)
Boost beforeEach
    ✔ Should generate CPFP for send transaction (2128ms)
Boost beforeEach
    ✔ Should generate RBF for send transaction (1967ms)

  Electrum Methods
Boost beforeEach
    ✔ connectToElectrum: Should connect to a random Electrum server (291ms)
Boost beforeEach
    ✔ isConnected: Should return true if connected to an Electrum server (47ms)
Boost beforeEach
    ✔ getAddressBalance: Should return the balance (in sats) of the provided address (314ms)
Boost beforeEach
    ✔ getNextAvailableAddress: Should return the next available address/change index and the last used address/change index (576ms)
Boost beforeEach
    ✔ Should return available UTXO's (3340ms)
 ...

After:

 Boost
Boost beforeEach
   ✔ Should fail in some cases. (2698ms)
Boost beforeEach
   ✔ Should generate CPFP for send transaction (2124ms)
Boost beforeEach
   ✔ Should generate RBF for send transaction (2105ms)

 Electrum Methods
Electrum before
   ✔ connectToElectrum: Should connect to a random Electrum server (299ms)
   ✔ isConnected: Should return true if connected to an Electrum server (295ms)
   ✔ getAddressBalance: Should return the balance (in sats) of the provided address (307ms)
   ✔ getNextAvailableAddress: Should return the next available address/change index and the last used address/change index (748ms)
   ✔ Should return available UTXO's (3794ms)