Rust errors/warnings in editor - `#![feature] may not be used on the stable release channel`

[matrixbot]

This issue has been migrated from #15706.

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In my editor (VSCode), the following errors/warnings are ever present and annoying to look at. Is there anyway to resolve these to not complain by default?

error[E0554]: `#![feature]` may not be used on the stable release channel
  --> rust/benches/glob.rs:15:12
   |
15 | #![feature(test)]
   |            ^^^^

I feel like the warning is a more new thing since I only remember the errors being there before.

unused import: `std::collections::BTreeSet`
`#[warn(unused_imports)]` on by default