chore: publish = false for pkgs not meant to be published

These tree packages are considered to be published something.
To reduce the logic of xtask-unpubilshed, let's flag them false for now.
We can always set it `true` when needed.

benches/capture/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.1.0"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 description = "Tool for capturing a real-world workspace for benchmarking."
+publish = false
 
 [dependencies]
 cargo_metadata.workspace = true

crates/cargo-test-macro/Cargo.toml

@@ -7,6 +7,7 @@ homepage = "https://github.com/rust-lang/cargo"
 repository = "https://github.com/rust-lang/cargo"
 documentation = "https://github.com/rust-lang/cargo"
 description = "Helper proc-macro for Cargo's testsuite."
+publish = false
 
 [lib]
 proc-macro = true

crates/cargo-test-support/Cargo.toml

@@ -3,6 +3,7 @@ name = "cargo-test-support"
 version = "0.1.0"
 license = "MIT OR Apache-2.0"
 edition = "2021"
+publish = false
 
 [lib]
 doctest = false