Use inline script instead actions-rs

[s7tya]

The repository for actions-rs/toolchain has been archived and is no longer maintained. Instead, this PR uses an inline script like:

      - name: Install stable toolchain
        run: |
          rustup install $RUST_TOOLCHAIN_VERSION --profile minimal
          rustup default $RUST_TOOLCHAIN_VERSION
          rustup component add --toolchain $RUST_TOOLCHAIN_VERSION rustfmt clippy
        env:
          RUST_TOOLCHAIN_VERSION: stable

Additionally, I've updated the versions for actions/checkout, actions/setup-node, and Swatinem/rust-cache.

[Kobzol]

Thank you! :)