Use prettyplease to format expectations (rust-lang#2536)

This PR replaces `rustfmt` by `prettyplease` as the used formatter for
the expectation tests.

This was done because we currently rely on the nightly version of
`rustfmt` which recently broke our test suite by changing how code in
macros is formatted. The `prettyplease` crate does not have that issue
because we are using a specific version in the Cargo manifest.

Author: pvdrz

Cargo.lock

@@ -10,6 +10,8 @@ diff = "0.1"
 shlex = "1"
 clap = { version = "4", features = ["derive"] }
 clap_complete = "4"
+prettyplease = { version = "0.2.0" }
+syn = { version = "2.0" }
 tempfile = "3"
 
 [features]

bindgen-tests/Cargo.toml

@@ -0,0 +1,2 @@
+# disable rustfmt for this crate so running `cargo fmt` doesn't affect the expected binding files
+disable_all_formatting = true