Use rust-cache instead of actions/cache for better CI performance

[TaKO8Ki]

Replace actions/cache with rust-cache

Motivation and Context

rust-cache (https://github.com/Swatinem/rust-cache) not only caches necessary files and directories such as ~/.cargo and target, but also removes unused dependencies before caching. Additionally, it disables incremental compilation CARGO_INCREMENTAL=0, which is unnecessary for CI environments.

rust-cache is used in large Rust open-source software projects such as axum and others.
ref: https://github.com/tokio-rs/axum/blob/cd2d5e1417e82b6fdc69c84847e438d9b37cd6a2/.github/workflows/CI.yml#L21

I confirmed that rust-cache works in an empty commit, which was removed.

... Restoring cache ...
Cache hit for: v0-rust-test-Linux-x64-c733e78c-c821e4bd
Received 134217728 of 288542975 (46.5%), 127.5 MBs/sec
Received 288542975 of 288542975 (100.0%), 153.9 MBs/sec
Cache Size: ~275 MB (288542975 B)

With caching, the execution time of the "Rust tests" job has been reduced from 1m 54s (without cache) to 1m 16s (with cache).

• With cache (1m 16s) https://github.com/modelcontextprotocol/rust-sdk/actions/runs/14146152574
• Without cache (1m 54s) https://github.com/modelcontextprotocol/rust-sdk/actions/runs/14146111023

How Has This Been Tested?

Breaking Changes

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

[jokemanfire]

LGTM， thanks.

[jokemanfire]

#49