feat(pool): Connection pool distinguishes request versions

[0x676e67]

This pull request introduces changes to the src/util/client/mod.rs file to include the HTTP version in the PoolKey struct and updates the related methods accordingly. Additionally, a new test has been added to verify the behavior of the client pool cache.

Changes to src/util/client/mod.rs:

• Added version field to PoolKey struct and updated the new method to include the version parameter.
• Updated the Dst::new method to accept the version parameter and pass it to PoolKey::new.
• Modified the Dst::new method to pass the version parameter to PoolKey::new when constructing a Dst instance.
• Updated the request method to extract the HTTP version from the request and pass it to the Dst::new method.
• Modified the request method to include the version parameter when calling Dst::new.

New test in tests/client.rs:

• Added pool_cache test to verify the behavior of the client pool cache with different HTTP versions.