Improve `CodeExecutor` (#2358)

Since `sp-state-machine` and `GenesisConfigBuilderRuntimeCaller` always
set `use_native` to be false.
We should remove this param and make `NativeElseWasmExecutor` behave
like its name.
It could make the above components use the correct execution strategy.

Maybe polkadot do not need about `NativeElseWasmExecutor` anymore. But
it is still needed by other chains and it's useful for debugging.

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Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: command-bot <>
Co-authored-by: Michal Kucharczyk <[email protected]>