fix(eth_senduseroperation): allow 0 for request ID & support gas limit markup

[TheDivic]

📖 Context

Type of change

• Non-breaking change (backwards compatible)

Why are we doing this?

• We incorrectly checked the JSON-RPC request ID, and it would generate a new request ID in case the client sent 0, and we should always return whatever the client sent.
• Gnosis estimate gas returns a low gas limit consistently.

What did we do?

• Check if the request ID is defined and not "truthy".
• Allow adding a markup (in wei) to the call gas limit returned from simulation to handle cases where the RPC doesn't return the correct estimate from eth_estimateGas (for example on Gnosis).