Introduce forking

[FabijanC]

Usage related changes

• Close Forking #195
• User instructions are in README.md under Forking
  • basically it's a subset of Devnet-py's CLI params, but the origin interaciton possibilities should be the same (if not better)
• In case of NoStateAtBlock, a wildcard error is returned instead of ContractError

Development related changes

• Add two forking structures: OriginForwarder and StarknetDefaulter (read more about them in the code docs)
• Use 6 parallel jobs in testing (previously had 7 - failing)
  • Related: CI workflow sometimes overuses memory #378
  • If Universal Sierra compiler #391 is merged before this PR, the conflict shall be resolved in favor of that PR
• Improve testing by adding utilities
  • e.g. BackgroundDevnet methods like create_block, fork, get_balance_at_block
• Two e2e tests interact with Sepolia.
• Replace StateHistoryDisabled error with NoStateAtBlock
• Add get_block_number method to timestamp.cairo testing contract and rename it to block_reader.cairo
• Refactor crates/starknet-devnet-server/src/api/json_rpc/mod.rs to call .to_rpc_result() in only one place.

Checklist:

• Applied formatting - ./scripts/format.sh
• No linter errors - ./scripts/clippy_check.sh
• No unused dependencies - ./scripts/check_unused_deps.sh
• Performed code self-review
• Rebased to the last commit of the target branch (or merged it into my branch)
• Documented the changes
• Linked the issues which this PR resolves
• Checked the TODO section in README.md if this PR resolves it
• Updated the tests
• All tests are passing - cargo test