fix: remove redundant U256::from on Host getters in instructions

[Forostovec]

• Replace U256::from(context.host.block_number()) with context.host.block_number() in block_info.rs.
• Replace U256::from(context.host.effective_gas_price()) with context.host.effective_gas_price() in tx_info.rs.
• Aligns with Host methods already returning U256 and matches style of adjacent instructions.

[codspeed-hq]

CodSpeed Performance Report

Merging #3053 will not alter performance

_{Comparing Forostovec:fix/remove-redundant-u256-from-host-getters (1470e60) with main (07953cd)}

Summary

✅ 173 untouched

[rakita]

lgtm