Add support for a new attribute #[debugger_visualizer] to support embedding debugger visualizers into a generated PDB.

Cleanup `DebuggerVisualizerFile` type and other minor cleanup of queries.

Merge the queries for debugger visualizers into a single query.

Revert move of `resolve_path` to `rustc_builtin_macros`. Update dependencies in Cargo.toml for `rustc_passes`.

Respond to PR comments. Load visualizer files into opaque bytes `Vec<u8>`. Debugger visualizers for dynamically linked crates should not be embedded in the current crate.

Update the unstable book with the new feature. Add the tracking issue for the debugger_visualizer feature.

Respond to PR comments and minor cleanups.

compiler/rustc_span/src/lib.rs

@@ -71,6 +71,7 @@ use std::hash::Hash;
 use std::ops::{Add, Range, Sub};
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
+use std::sync::Arc;
 
 use md5::Digest;
 use md5::Md5;
@@ -1200,6 +1201,28 @@ impl SourceFileHash {
     }
 }
 
+#[derive(HashStable_Generic)]
+#[derive(Copy, PartialEq, PartialOrd, Clone, Ord, Eq, Hash, Debug, Encodable, Decodable)]
+pub enum DebuggerVisualizerType {
+    Natvis,
+}
+
+/// A single debugger visualizer file.
+#[derive(HashStable_Generic)]
+#[derive(Clone, Debug, Hash, PartialEq, Eq, PartialOrd, Ord, Encodable, Decodable)]
+pub struct DebuggerVisualizerFile {
+    /// The complete debugger visualizer source.
+    pub src: Arc<[u8]>,
+    /// Indicates which visualizer type this targets.
+    pub visualizer_type: DebuggerVisualizerType,
+}
+
+impl DebuggerVisualizerFile {
+    pub fn new(src: Arc<[u8]>, visualizer_type: DebuggerVisualizerType) -> Self {
+        DebuggerVisualizerFile { src, visualizer_type }
+    }
+}
+
 /// A single source in the [`SourceMap`].
 #[derive(Clone)]
 pub struct SourceFile {