Optimization: Modify `Heap` read and write related functions (wip)

[JulianVentura]

Description

This PR improves vm performance by updating Heap read and write related functions.

Inspiration

We are currently iterating and applying U256 operations with a for loop on some Heap functions, like read. It works, but it's not very efficient. We may replace this with functions like U256::from_big_endian instead.

Changes

• Heap::store
• Heap::read
• Heap::expanded_read
• Heap::read_unaligned_from_pointer

Results

• Up to 45% improvement on bench heap_read_write.
• Around 5% improvement on the other benches.
• Around 11% improvement on execution time running all but event_spam benches.

[JulianVentura]

Close because moved to #216