Short-circuit address parsing on hot path during block processing

[pragmaxim]

Summary Of Changes

• Speed up padded address parsing in addressFromPaddedHex by decoding the last 20 bytes directly when the input is a 32-byte padded topic or calldata slot, and fall back to big.Int only for odd formats.
• Add unit tests that cover padded, unpadded, and invalid inputs for addressFromPaddedHex.

addressFromPaddedHex: What Was Wrong And How It Was Fixed

• Problem: The original implementation always parsed the full hex string into a big.Int. For topics and calldata, addresses are 32-byte padded, so most of that work was wasted and done on every transfer/log.
• Fix: Strip optional 0x, fast-path decode the last 40 hex characters (20 bytes) via hex.DecodeString and BytesToAddress, and fall back to the original big.Int parse only when the fast path does not apply or fails.