Add READ_ONLY flag to contract call function (#4418)

This PR implements the `READ_ONLY` flag to be used as a `Callflag` in
the `call` function.
The flag indicates that the callee is restricted from modifying the
state during call execution.
It is equivalent to Ethereum's
[STATICCALL](https://eips.ethereum.org/EIPS/eip-214).

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Co-authored-by: command-bot <>
Co-authored-by: Andrew Jones <[email protected]>
Co-authored-by: Alexander Theißen <[email protected]>