add support for fuzzing · rust-lang/a-mir-formality@c561075

The following actions uses node12 which is deprecated and will be forced to run on node16: actions-rs/cargo@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

The following actions uses Node.js version which is deprecated and will be forced to run on node20: actions-rs/cargo@v1. For more info: https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/

unnecessary parentheses around pattern

`formality-macros` (lib) generated 1 warning (run `cargo fix --lib -p formality-macros` to apply 1 suggestion)

`formality-rust` (lib) generated 1 warning (run `cargo fix --lib -p formality-rust` to apply 1 suggestion)

`a-mir-formality` (lib) generated 1 warning

unnecessary parentheses around pattern

`formality-macros` (lib) generated 1 warning (run `cargo fix --lib -p formality-macros` to apply 1 suggestion)

unused import: `ValueGenerator`

unused `#[macro_use]` import

`formality-rust` (lib) generated 1 warning (run `cargo fix --lib -p formality-rust` to apply 1 suggestion)

`a-mir-formality` (lib) generated 1 warning

`formality-rust` (lib test) generated 1 warning (1 duplicate)

unnecessary parentheses around pattern

1 warning emitted

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