Class TxHelpers Revision (April 11)

[barakman]

This PR includes several changes, mostly around coding simplification and performance improvements in the TxHelpers class, alongside a few related or partially-related cleanups in other modules.

The main changes in the TxHelpers class are listed below, and only two of them - 1 and 6 - are expected to impact the actual Arb-Behavior of the bot:

1. Replace the user-configurable DEFAULT_GAS_PRICE_OFFSET constant with a gas_strategy function.
2. Fetch the maxPriorityFee via web3 instead of by sending an HTTP request to the node.
3. Fetch the gasPrice instead of fetching the entire block in order to retrieve the baseFee.
4. Send a single gas-estimation request to the node.
5. Fetch the accessList via web3 instead of by sending an HTTP request to the node.
6. Remove the EXPECTED_GAS_MODIFIER constant used for producing an optimistic gas consumption.
7. Remove support for legacy-transactions; all chains are assumed to be supporting EIP-1559.
8. Send eth_sendPrivateTransaction HTTP requests via web3 instead of via the node.
9. Ensure that the access list is applied on Ethereum transactions; it is not applied in the current version due to a bug in the code, and even after this PR, it will not be tested within Tenderly (when the target chain is Ethereum) because of that same bug; see issue NETWORK_TENDERLY overrides the original NETWORK #519.
10. Construct the tx dictionary manually and then set its gas attribute by calling estimate_gas, instead of doing both of these things via build_transaction; following that, set the accessList attribute in this dictionary, and possibly update its gas attribute, by calling create_access_list; the gas-fee attributes (maxFeePerGas and maxPriorityFeePerGas) are set only at the end, in order to avoid getting the "max fee per gas less than block base fee" error.

Handled all comments