feat: derive Hash for evm_rpc_types hex wrappers

[sueun-dev]

Fixes #393.

What changed:

• Derived Hash for the evm_rpc_types hex wrappers generated by impl_hex_string!.
• Derived Hash for the internal Byte wrapper so HexByte is covered too.
• Added regression coverage for Hex20 as a HashMap key and HexByte, Hex32, Hex256, and Hex in HashSets.

Why:
These wrappers already compare by decoded bytes through Eq, so hashing the same inner values is consistent with their equality behavior. This lets callers use hash-based collections when they need them without changing Candid, serde, display, or parsing behavior.

Checked:

• cargo test -p evm_rpc_types
• cargo test -p evm_rpc_types --all-features

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR enables Ethereum hex-string wrapper types to be used as keys in hash-based collections by deriving Hash, and adds a unit test that exercises HashMap/HashSet usage for several hex types.

Changes:

• Derive Hash for all hex-string wrapper types generated by impl_hex_string!.
• Derive Hash for Byte.
• Add a test validating Hex20, Hex32, HexByte, Hex, and Hex256 can be used in HashMap/HashSet.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
evm_rpc_types/src/tests.rs	Adds a new unit test that checks hex wrapper types work as hash keys/values in HashMap/HashSet.
evm_rpc_types/src/lib.rs	Adds Hash derives to hex wrapper types and Byte to support usage in hash-based collections.

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[gregorydemay]

Thanks for this PR @sueun-dev !