feat: introduce gas_floor_base_cost for EIP-7623 compliance

[aleksuss]

Summary by CodeRabbit

• New Features

  • Added gas floor calculation support with configurable base cost, enabling more precise gas accounting across network upgrades. Gas floor base cost is set to 21,000 for Prague and 0 for other forks.

• Refactor

  • Optimized gas computation logic by consolidating floor gas calculation into a dedicated helper function.

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Walkthrough

The changes introduce a new gas_floor_base_cost configuration field to the runtime's Config struct and propagate it across hard-fork initializers. A helper function is extracted in the gasometer module to consolidate floor gas computation logic, with a clippy lint suppression added.

Changes

Cohort / File(s)	Summary
Configuration infrastructure evm/src/runtime/mod.rs	Added public field gas_floor_base_cost: u64 to both Config and DerivedConfigInputs structs. Propagated through all hard-fork initializers (frontier, istanbul, berlin, london, merge, shanghai, cancun, prague), with prague() setting the value to 21000 and others defaulting to 0.
Gas calculation refactoring evm/src/gasometer/mod.rs	Extracted local helper function floor_gas_calc inside intrinsic_gas_and_gas_floor to consolidate repeated floor gas calculation logic. Applied clippy lint suppression #[allow(clippy::as_conversions)] to the public function.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 The gasometer hops with glee,
Floor calculations merged so clean,
Config spreads from fork to fork,
A rabbit's refactoring work! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: introducing gas_floor_base_cost parameter for EIP-7623 compliance, which aligns with the PR objectives and the changes across two files.

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[aleksuss]

@CodeRabbit full review

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✅ Actions performed

Full review triggered.

[birchmd]

Maybe we should use saturating arithmetic operations here just to be safe.

[aleksuss]

Good idea 👍🏻