use tokio::fs for all filesystem operations

[KSXGitHub]

https://docs.rs/tokio/latest/tokio/fs/index.html

[anonrig]

I remember reading an article about tokio::fs is slower than std::fs. Ref: https://users.rust-lang.org/t/why-tokio-fs-is-slower-than-std-fs/39610

[KSXGitHub]

I remember reading an article about tokio::fs is slower than std::fs. Ref: https://users.rust-lang.org/t/why-tokio-fs-is-slower-than-std-fs/39610

The async code in the link is slow is because there is no parallelization. The author called .await serially on each entry.

Again. As with all things, we need to benchmark to find out.