feat: add sload op (bus-mapping version)

[0xmountaintop]

privacy-ethereum/zkevm-specs#106

Notes:

1. would like to separate sload and sstore PR. because the gas calculation and the TxRefund calculation for sstore are more complicated.
2. non-bus-mapping version: feat: add sload op (non-bus-mapping version) #334

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Since the bus-mapping version tests cannot really cover 1) is_warm 2) reverted cases, I just keep both "bus-mapping" and "handwrite rw_table" versions.

[ChihChengLiang]

Can we also rebase and squash some commits for reviewability?

[CPerezz]

If it's not ready for review also, can we set it as WIP? And put the PR as draft?

[0xmountaintop]

It can be reviewed. it's just a different version of #334 and I am not sure which version is preferred.

But if "rebase/squash" before review is preferable as @ChihChengLiang suggests, I can turn it to WIP or draft.

[CPerezz]

It can be reviewed. it's just a different version of #334 and I am not sure which version is preferred.

But if "rebase/squash" before review is preferable as @ChihChengLiang suggests, I can turn it to WIP or draft.

So we should review both and decide? What do they differ on?
For me, we can add the non-bus-mapping version and file an issue for the test addition once #349 is merged.

That PR will allow to build the tests you need.

[0xmountaintop]

For me, we can add the non-bus-mapping version and file an issue for the test addition once #349 is merged.

That PR will allow to build the tests you need.

Sounds good, I will close this for now.