Delete the standalone funtions in ev-prover lib.rs when unused

[damiannolan]

Description

We should aim to delete the functions in lib.rs of ev-prover.

As far as I know most of them should now live on the ChainContext struct, so we can remove this file
https://github.com/celestiaorg/celestia-zkevm/blob/main/crates/ev-prover/src/lib.rs