ci: add rust cache to turbo test workflow

[devin-ai-integration]

Description

Add Rust caching to the turbo test workflow to improve CI performance.

This PR:

• Adds Rust caching using Swatinem/rust-cache@v2
• Follows the same pattern as other Rust workflows in the repository
• Does not modify the turbo build workflow as it doesn't use Rust

Link to Devin run: https://app.devin.ai/sessions/6e20ec2b71cf44168007a02b34cb18be
Requested by: Jayant

[devin-ai-integration]

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[cprussin]

Pleas remove the self-references in the files section in each action as thy are not necessary