[WIP] Support lint level configuration in clippy.toml

[odysa]

changelog: Add support for lint level configuration in clippy.toml

Fixes #15128

Add support for configuring lint levels in clippy.toml using the same format as Cargo.toml. This allows users to move lint configurations from Cargo.toml to clippy.toml to keep dependency management and linting separate.

Example

clippy.toml:

[lints.clippy]
needless_return = "allow"
single_match = { level = "warn", priority = 5 }

[lints.rust]
dead_code = "allow"