feat: gastime package

[ARR4N]

Introduces the gas clock, an extension of a proxytime.Time[gas.Gas] that also tracks a "continuous" equivalent of ACP-176 gas excess at gas-unit resolution instead of per second.

Closes #11

[Copilot]

Pull Request Overview

This PR introduces a new gastime package that implements a "gas clock" - a time measurement system based on gas consumption rather than traditional time units. The implementation extends proxtime.Time[gas.Gas] to track both time passage and a continuous equivalent of ACP-176 gas excess at gas-unit resolution.

Key changes:

• Gas-based time tracking with excess consumption monitoring per ACP-176/194
• Canoto serialization support for persistence and network transmission
• Comprehensive test coverage for scaling operations and excess calculations

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
go.mod	Adds uint256 dependency for geth/libevm compatibility
gastime/gastime.go	Core Time struct with gas-based time tracking and excess management
gastime/marshal.go	Canoto serialization interface and marshaling methods
gastime/marshal.canoto.go	Generated canoto marshaling implementation
gastime/gastime_test.go	Comprehensive tests for scaling, excess calculations, and cloning
gastime/cmpopt.go	Test utilities for comparing Time instances

[StephenButtolph]

Really my only questions/concerns are cases of potential overflow.