add clippy and rustfmt components to rust-toolchain.toml

[DetachHead]

Summary

prevents this error when running ./test.py --fmt or ./test.py --lint:

$ ./test.py --fmt
Running formatting...
error: 'cargo-fmt' is not installed for the toolchain 'stable-x86_64-unknown-linux-gnu'
To install, run `rustup component add rustfmt`

Test Plan

$ ./test.py --fmt
Running formatting...
info: syncing channel updates for 'stable-x86_64-unknown-linux-gnu'
info: latest update on 2026-09-03, rust version 1.98.1 (48a229cea 2026-09-01)
info: downloading component 'clippy'
info: downloading component 'rustfmt'
info: installing component 'clippy'
info: installing component 'rustfmt'

[meta-codesync]

@stroxler has imported this pull request. If you are a Meta employee, you can view this in D118959748. (Because this pull request was imported automatically, there will not be any future comments.)