Factor out clippy_utils crate

Author: smoelius

.gitignore

@@ -18,6 +18,7 @@ out
 *Cargo.lock
 /target
 /clippy_lints/target
+/clippy_utils/target
 /clippy_workspace_tests/target
 /clippy_dev/target
 /rustc_tools_util/target

clippy_lints/Cargo.toml

@@ -18,6 +18,7 @@ edition = "2018"
 
 [dependencies]
 cargo_metadata = "0.12"
+clippy_utils = { path = "../clippy_utils" }
 if_chain = "1.0.0"
 itertools = "0.9"
 pulldown-cmark = { version = "0.8", default-features = false }