fix(memory_instance): zero out heap memory when reallocating after reset

[rymnc]

[Link to related issue(s) here, if any]

• none

[Short description of the changes.]

• we zero out the dirty memory when reallocating the heap. this is only detectable after a reset.

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
  • we need to do this
• 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?

[MitchTurner]

nit: Can we name these macros:
generate_tests__memory_instance__grow_heap_by_after_reset__does_not_retain_dirty_memory_size
and
generate_test__memory_instance__grow_heap_by_after_reset__does_not_retain_dirty_memory_size
or something that makes it abundantly clear that these macros are generating tests. It's just not the expected format as a reader.

I wish there was a way to do this with prop_test, but you need to know the sizes at compile time, so I don't think that's supported.

[rymnc]

I wish there was a way to do this with prop_test, but you need to know the sizes at compile time, so I don't think that's supported

exactly why I went with this approach

[rymnc]

addressed in 868938d