op-chain-ops: legacy withdrawal script refactoring

[tynes]

Description

Clean up the script that is used to migrate legacy withdrawals.
This script is very important for testing the legacy withdrawal
migration.

A bug was introduced with #4911
which was a sherlock audit fix. This was a bug because the change
resulted in the withdrawal hashes changing, meaning that the storage
slots computed client side also changed. This resulted in breaking the
script. This commit reverts this change. The changes landing in
#5470 will cause the
buffer in the gas limit for the migrated withdrawals to be too small,
so we can reintroduce this code behind a switch with the network.
Its not ideal that the migration code isn't going to match 1:1
with goerli but thats ok because we will be able to thoroughly
test it.

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Latest commit: 0ac98a2

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[tynes]

If these fixes are merged and then #5459 is rebased on top of this, it should fix @roninjin10's issue. Will need to actually see it work but feeling pretty sure that the combo of these fixes will work

[roninjin10]

Amazing!

[mslipper]

Is this a pure revert, or was additional functionality introduced?

[tynes]

Is this a pure revert, or was additional functionality introduced?

I left in the unit tests and modularization that enabled the unit tests but the underlying functionally was reverted

[tynes]

Can I get a review from @ethereum-optimism/ecopod ?

[mergify]

This PR has been added to the merge queue, and will be merged soon.

[mergify]

This PR is next in line to be merged, and will be merged as soon as checks pass.