Replace #[allow(lint)] with #[expect(lint)]

[lrh2000]

#[expect(lint)] has been stabilized for a while. We should use it instead of #[allow(lint)] whenever possible. RFL's coding guidelines explains why:

On top of that, Rust provides the expect attribute [..]. It makes the compiler warn if the warning was not produced. [..]

This means that expects do not get forgotten when they are not needed, [..]

Thus prefer expect over allow unless [..]

In this PR, I have removed all obsolete #[allow(lint)] and replaced the remaining #[allow(lint)] with #[expect(lint)].

I'm also trying to globally enable the allow_attributes lint to prevent #[allow(lint)] from being added inadvertently in the future. I'm trying to figure out what is the best way for us to globally enable lint¹.

First, I enabled the lint in the workspace:

# In `/Cargo.toml`:

[workspace.lints.clippy]
allow_attributes = "warn"

Then every crate in the workspace could be made to respect the lint configuration:

# In `/kernel/Cargo.toml`:

[lints]
workspace = true

However, I could not get such settings to be automatically added to crates outside the workspace (i.e., OSDK and those under kernel/libs/comp-sys). I left such crates as they were:

asterinas/Cargo.toml

Lines 37 to 47 in 56b85cb

	exclude = [
	"kernel/libs/comp-sys/cargo-component",
	"kernel/libs/comp-sys/component",
	"kernel/libs/comp-sys/component-macro",
	"kernel/libs/comp-sys/controlled",
	"osdk",
	# The `base` and `test-base` crates are auto-generated by OSDK and ultimately built by Cargo
	# during `cargo osdk run` and `cargo osdk test` commands
	"target/osdk/base",
	"target/osdk/test-base",
	]

Footnotes

1. This is useful for us because it can help us deal with other lints in the future. For example, Rust 2024 is coming, so we may try to globally enable the rust-2024-compatibility lint group soon. ↩

[tatetian]

LGTM. Thanks for the contribution!