Add `bytes_to_packed_u32_felts()` function to utils module

[partylikeits1983]

Problem

The ethereum_address_to_felts() function manually converts bytes to packed u32 felts, but miden-vm already has a general helper function [bytes_to_packed_u32_felts()] that does exactly this conversion.

bytes_to_packed_u32_felts: https://github.com/0xMiden/miden-vm/blob/e37729eacdd56fc53aa372aa441ef835eb18bb45/crates/lib/core/src/handlers/mod.rs#L191

Context: #2023 (comment)

Solution

Add the bytes_to_packed_u32_felts() function to the utils module in miden-base and refactor ethereum_address_to_felts() to use this general helper instead of the current manual implementation.

Benefits

• Reduces code duplication
• Uses a proven, tested implementation
• Makes the conversion logic more maintainable
• Provides a reusable utility for other byte-to-felt conversions

[mmagician]

closed in #2359