Suggestion: use rust-version field

[hellow554]

Description

There is a "new" field in the Cargo.toml that can be used to specify the minimum supported rust version: rust-version

This feels somewhat redundant to the msrv in the clippy.toml file: https://github.com/rust-lang/rust-clippy/blob/master/README.md#specifying-the-minimum-supported-rust-version

If I see it correctly, clippy currently ignores the rust-version field from Cargo.toml.

Would it be a good approach to take that field into account when searching for a msrv?

Version

rustc 1.62.0-nightly (18f314e70 2022-04-24)
binary: rustc
commit-hash: 18f314e7027fe7084aaab8620c624a0d7bd29e70
commit-date: 2022-04-24
host: x86_64-unknown-linux-gnu
release: 1.62.0-nightly
LLVM version: 14.0.1

Additional Labels

@rustbot modify labels: A-clippy T-cargo