Prefer Unstructured Storage for Upgradeable Contracts

Linear storage, which is the default way to manage storage variables, is intuitive but has limitations. When combined with inheritance, it requires us to maintain the well-known (and some would say infamous) __gap array. Managing this array increases complexity and makes audits more challenging.

A proposed alternative is to use EIP-7201 storage slots, which can offer greater flexibility. However, this approach should be used with caution: variable names should be uniquely chosen and consistently referenced. Utilizing spelling checkers can help maintain naming consistency and reduce potential issues.