ci(caches): use rust-cache instead of buildjet to cache deps

[rymnc]

Linked Issues/PRs

• none

Description

After looking at a lot of CI runs, noticed the buildjet caches are not operating as intended. our external deps are compiled every single time. I have used Swatinem/rust-cache@v2 before, and in https://github.com/fuellabs/zkvm-primitives

Checklist

• Breaking changes are clearly marked as such in the PR description and changelog
• New behavior is reflected in tests
• 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?

[rymnc]

some larger issue with the caches, closing as deprioritising for now