Fix clippy warnings pr

[dan-da]

Addresses #45

• Fixes clippy warnings about unnecessary vec![] and Arc<RefCell<..>>
• Applies cargo fmt

With this patch applied, both these commands run cleanly:

$ cargo clippy --all-features --all-targets
$ cargo fmt --check

Notes:

• running cargo version 1.72.0 (103a7ff2e 2023-08-15)
• Changed all occurences of Arc<RefCell<..>> to Arc<Mutex<..>>. These were only in the Dashboard.

Testing:

• Verified that Dashboard runs and navigated all screens
• ran cargo test without error

[Sword-Smith]

Yeah. Since the dashboard has a polling thread and is apparently multi threaded, I guess we need Arc and not just Rc there.

The rest of the commits I consider uncontroversial. Thanks for fixing this though.