Add slither for l1 contracts

[dnkolegov]

What ❔

This PR enables the slither static analyzer for L1 contracts and also resolves the issues it has found.
It is configured to catch high- and medium-severity potential issues.
It doesn't check Verifier.sol contract.

The PR also documents how to deal with findings.

Why ❔

To find "low-hanging fruits" bugs and known vulnerabilities.

Checklist

• PR title corresponds to the body of PR (we generate changelog entries from PRs).
• Tests for the changes have been added / updated.
• Documentation comments have been added / updated.

[dnkolegov]

@StanislavBreadless as we discussed with @vladbochok could you please review the following findings

MailboxFacet._deriveL2GasPrice(uint256,uint256) (contracts/state-transition/chain-deps/facets/Mailbox.sol#163-182) performs a multiplication on the result of a division:
	- l1GasPriceConverted = (_l1GasPrice * s.baseTokenGasPriceMultiplierNominator) / s.baseTokenGasPriceMultiplierDenominator (contracts/state-transition/chain-deps/facets/Mailbox.sol#[16](https://github.com/matter-labs/era-contracts/actions/runs/8425289708/job/23071021468?pr=280#step:9:17)6-167)
	- batchOverheadBaseToken = uint256(feeParams.batchOverheadL1Gas) * l1GasPriceConverted (contracts/state-transition/chain-deps/facets/Mailbox.sol#173)
MailboxFacet._deriveL2GasPrice(uint256,uint256) (contracts/state-transition/chain-deps/facets/Mailbox.sol#163-182) performs a multiplication on the result of a division:
	- l1GasPriceConverted = (_l1GasPrice * s.baseTokenGasPriceMultiplierNominator) / s.baseTokenGasPriceMultiplierDenominator (contracts/state-transition/chain-deps/facets/Mailbox.sol#166-167)
	- pubdataPriceBaseToken = L1_GAS_PER_PUBDATA_BYTE * l1GasPriceConverted (contracts/state-transition/chain-deps/facets/Mailbox.sol#[17](https://github.com/matter-labs/era-contracts/actions/runs/8425289708/job/23071021468?pr=280#step:9:18)0)
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#divide-before-multiply

and let us know how we should proceed. Should it be fixed or ignored? If fixed, then could you add a fix into this PR?
Thank you.

[StanislavBreadless]

@dnkolegov we can ignore it. If we used what slither proposed, the calculations would indeed be slightly more precise, but IMHO the way it is now is a bit easier to read & reuse (i.e. whenever we need l1 gas price we can use l1GasPriceConverted)