feat: setup configuration for upcoming hard fork and re-enable sha256 precompile

[NazariiDenha]

1. Purpose or design rationale of this PR

1. We have a range of breaking features coming up. We will enable most of these as part of the next (yet unnamed) hard fork in about 3 months.

In order to be able to add these features to l2geth without breaking compatibility with our current networks, we need to add a fork number / timestamp configuration, similarly to how we activated Archimedes. We can activate the new fork at block 0 on new testnets, while on Scroll and Scroll Sepolia the activation block number will be determined later.
https://app.asana.com/0/1202293017617135/1205896809138433/f

2. Re-enable sha256 precompile.

In the Archimedes hard fork we disabled the SHA-256 precompile. In the next hard fork, we want to re-enable it.
https://app.asana.com/0/1202293017617135/1205896809138436/f

2. PR title

Your PR title must follow conventional commits (as we are doing squash merge for each PR), so it must start with one of the following types:

• build: Changes that affect the build system or external dependencies (example scopes: yarn, eslint, typescript)
• ci: Changes to our CI configuration files and scripts (example scopes: vercel, github, cypress)
• docs: Documentation-only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that doesn't fix a bug, or add a feature, or improves performance
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
• test: Adding missing tests or correcting existing tests

3. Deployment tag versioning

Has the version in params/version.go been updated?

• This PR doesn't involve a new deployment, git tag, docker image tag, and it doesn't affect traces
• Yes

4. Breaking change label

Does this PR have the breaking-change label?

• This PR is not a breaking change
• Yes

[Thegaram]

Looks good. Can we find a better placeholder name than "Hardfork"? Let's use "Kepler" for now (might rename it later).

[NazariiDenha]

Looks good. Can we find a better placeholder name than "Hardfork"? Let's use "Kepler" for now (might rename it later).

ok, just didn't know how to name it