Rollback memory changes

[xgreenx]

This PR change the function diff that allowed to get changes between two arbitrary VM instances to a rollback_to function that allow to pass from current VM state to a previous one.

This restriction allow us to manage the memory that grows between instances because the current system wasn't working with memory that could grow but only with fixed size memory.

Checklist

• Breaking changes are clearly marked as such in the PR description and changelog
• New behavior is reflected in tests
• If performance characteristic of an instruction change, update gas costs as well or make a follow-up PR for that
• The specification matches the implemented behavior (link update PR if changes are needed)

Before requesting review

• I have reviewed the code myself
• I have created follow-up issues caused by this PR and linked them here

After merging, notify other teams

[Add or remove entries as needed]

• Rust SDK
• Sway compiler
• Platform documentation (for out-of-organization contributors, the person merging the PR will do this)
• Someone else?

[xgreenx]

Approved=)

[Voxelot]

Took me a while to wrap my head around all the heap pointer magic, but lgtm after writing a few of my own tests to sanity check.