Add events conversion for stateful precompiled contracts

[fbac]

The stateful precompiled contracts define the following function to preserve state:

ExecuteNativeAction(contract common.Address, converter statedb.EventConverter, action func(ctx sdk.Context) error) error

The converter is an object that converts cosmos-sdk events into eth events, such as in this implementation.

Implement a way of handling this conversion. The implemention will need:

• events
• decoders