CLI: Support --referenceBuildInfoDirs option

[ericglau]

In some project setups, users of the Upgrades Core CLI may not want to change the names of upgradeable contracts for every new version that they deploy. Instead, they just change the source code and want to perform storage layout comparisons with a previous version of their repository (e.g. from a different branch).

This PR provides a --referenceBuildInfoDirs option that takes a comma-separated list of additional build info directories that can be referenced for storage layout comparisons. These build info directories can be built from previous versions of the project repository, containing the build artifacts (including storage layouts) of previously deployed versions of contracts.

When using this option, refer to one of these directories using prefix <dirName>: before the contract name or fully qualified name in the --reference option or @custom:oz-upgrades-from annotation, where <dirName> is the directory short name. Each directory short name must be unique.

Example usage:

1. From an older branch containing previously deployed versions of contracts, compile the contracts with storage layouts and save a copy of the resulting build-info directory (defaults are artifacts/build-info for Hardhat projects or out/build-info for Foundry projects), renaming it to a unique name. For example, build-info-v1.
2. From the current branch containing the new versions of contracts that you want to upgrade to, compile the contracts with storage layouts for the new versions.
3. If you want to compare the storage layout of a contract called MyContract with its previous version, run the CLI command like:

npx @openzeppelin/upgrades-core validate --referenceBuildInfoDirs /old-builds/build-info-v1 --contract MyContract --reference build-info-v1:MyContract

Fixes #1034

[Amxx]

Lot to look at, and difficult to keep track when you are not familiar with the CLI's code, but it looks good to me !