Impl eth_call state override feature

[Pana]

This change is 

[ChenxingLi]

Reviewed 11 of 18 files at r1, all commit messages.
Reviewable status: 11 of 18 files reviewed, 4 unresolved discussions (waiting on @Pana)

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crates/cfxcore/executor/src/state/overlay_account/mod.rs line 187 at r1 (raw file):

    /// Inditcates if this account's storage entries and lazily loaded fields on
    /// db are marked invalid (so an entry is empty if not in cache).
    pub fn fresh_storage(&self) -> bool {

fresh_storage should take storage_overrided into consideration.

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crates/cfxcore/executor/src/state/state_object/state_override.rs line 26 at r1 (raw file):

            };

            self.prefetch(&addr_with_space, RequireFields::Code)?;

I think the following logic should be in the initialization of OverlayAccount, by adding a function like new_loaded_with_overrided, rather than repeatedly modifying the OverlayAccount here through state.

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crates/cfxcore/executor/src/state/overlay_account/storage.rs line 201 at r1 (raw file):

        Ok(if let Some(value) = self.cached_entry_at(key) {
            value
        } else if self.fresh_storage() || self.storage_overrided {

Update fresh_storage and remove this.

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crates/cfxcore/executor/src/state/overlay_account/storage.rs line 245 at r1 (raw file):

    // used for state override.diff
    pub fn update_storage_read_cache(&mut self, key: Vec<u8>, value: U256) {
        let owner = if self.address.space == Space::Native {

Assert empty checkpoint here.