Sample PR to develop

[vcastellm]

This contains the base example of the modifications to be done to work with build contraints.

• We'll need to adapt the build system to use: go build -tags validium cmd/
• We should not find any conflict when merging from upstream, so no history rewrite for upstream commits, and the PRs should just update cleanly.
• We need to create a merge script where all files received from upstream will overwrite the corresponding _validium.go files on our repo, so a new PR with these changes should show the diff of what's updated in upstream vs our implementation. This is an example of how it should looks like Update aggregator #99
• The only requirement is that the zkevm team, allows us to include the //go:build !validium tag on some specific go files.