Key Management Strategy Handler: Moar strategies

[T-Dnzt]

Hot wallets private keys first implementation only support the storage of the encryption key inside an environment variable. This feature involves adding more storage adapters and updating the blockchain wallet to know which adapter it is using. The needed adapters are:

• Encryption key in Environment variable (the logic should be extract into its own module if it hasn't been yet), private keys in DB
• Encryption key in file, private keys in DB
• Encryption key in file, private keys in files
• No Encryption key, private keys in KMS (GCP, AWS)