Extend EvmAddress::FromStr to accept addresses without 0x prefix

[venilinvasilev]

Description

Enhance EvmAddress::from_str to support parsing EVM address string
representations both with and without the 0x prefix.

Motivation

Many tools and user inputs provide hexadecimal addresses without the
0x prefix. Supporting both formats improves developer ergonomics and
ensures better compatibility across ecosystems.

Proposed Behavior

• Accept hexadecimal address strings with 0x prefix
• Accept hexadecimal address strings without 0x prefix
• Normalize input prior to validation and decoding

Acceptance Criteria

• Parsing succeeds for valid prefixed and non-prefixed inputs
• Existing prefixed behavior remains unchanged
• Unit tests cover both formats