ECAL opcode support

[zees-dev]

Description

The ECAL opcode is supported in fuel-vm to extend the capabilities of the VM.
Users can implement rust code to interop with the VM using the ECAL opcode.
This PR introduces support for the opcode in the sway repo - such that sway assembly can be successfully compiled with the ECAL opcode.

Examples of how to utilize the ECAL opcode can be seen here: https://github.com/FuelLabs/fuel-vm/blob/9478991db1ea8799fab47ebe1c195946a2698a7f/fuel-vm/examples/external.rs#L51

• Closes Add support for ECAL instruction #5239
• Added an e2e test to validate compilation of ecall opcode in sway assembly.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[codspeed-hq]

CodSpeed Performance Report

Merging #6947 will not alter performance

_{Comparing zees-dev/ecall-opcode (6a01732) with master (b07d0ca)}

Summary

✅ 22 untouched benchmarks

[sdankel]

Thanks!