Remove and dedupe `ethers-rs` vendored code

[Evalir]

Some code got vendored on #5986 to decouple types from ethers. Namely:

• Numeric type to parse different types of numbers (percentages, decimals, hex strings): These should either be deduped into a single Numeric type we can use everywhere and either upstream to alloy or centralize in common.
• format_units: This utility should eventually be upstreamed to Alloy primitives due to its usefulness.

[Evalir]

Closing—this was recently removed and added to alloy