Rollup merge of #65363 - Centril:less-pprust, r=Mark-Simulacrum

Remove implicit dependencies on syntax::pprust

Part of https://github.com/rust-lang/rust/pull/65324.

The main goal here is to facilitate the eventual move of pprust out from libsyntax and because an AST definition typically should not depend on its pretty printer.

r? @estebank

src/librustc/lint/levels.rs

@@ -12,6 +12,7 @@ use rustc_data_structures::stable_hasher::{HashStable, ToStableHashKey, StableHa
 use syntax::ast;
 use syntax::attr;
 use syntax::feature_gate;
+use syntax::print::pprust;
 use syntax::source_map::MultiSpan;
 use syntax::symbol::{Symbol, sym};
 
@@ -285,7 +286,7 @@ impl<'a> LintLevelsBuilder<'a> {
                             tool_ident.span,
                             E0710,
                             "an unknown tool name found in scoped lint: `{}`",
-                            meta_item.path
+                            pprust::path_to_string(&meta_item.path),
                         );
                         continue;
                     }