Explore combining `vm.PrecompileEnvironment` and `vm.OperationEnvironment`

[ARR4N]

They're already quite similar and are subject to the same nuances around security if introducing access to call other contracts.

Tip

If introducing access to EVM.*Call*() methods, it can be done in the same way as StateDB() is (dependent on the value of ReadOnly().

[ARR4N]

Redundant as now done in the PR that introduces vm.OperationEnvironment, #30.