Accept devnet/localhost node URLs

[dcorral]

What this PR does / why we need it:

• IMPORTANT: NODE_URL secret is mandatory and must include a trailing '/' i.e http://localhost:port/
• Tests can point to http://localhost:port URL skipping Basic Auth header if not required.
• Ability to set the target URL to a public or local endpoint not implementing Basic Auth. This is the case of devnet public endpoint ATM.

To fix:

• TestConnection_Call_Simple_Contract
• TestConnection_Get_Accounts
• TestConnection_Get_Balance
• TestConnection_GetTransactionCount
• TestConnection_EstimateGas
• TestConnection_MaxPriorityFeePerGas
• TestConnection_GasPrice
• TestConnection_NetVersion
• TestConnection_ChainId
• TestConnection_SendRawTransactionInValidEmpty
• TestConnection_SendRawTransactionInValidOldNonce
• TestConnection_FutureBlockByNumber
• TestConnection_InvalidBlockByHash
• TestConnection_InvalidTransactionByHash