Auto merge of #149709 - Urgau:overhaul-filenames, r=davidtwco

Overhaul filename handling for cross-compiler consistency

This PR overhauls the way we handle filenames in the compiler and `rmeta` in order to achieve achieve cross-compiler consistency (ie. having the same path no matter if the filename was created in the current compiler session or is coming from `rmeta`).

This is required as some parts of the compiler rely on consistent paths for the soundness of generated code (see rust-lang/rust#148328).

In order to achieved consistency multiple steps are being taken by this PR:
 - by making `RealFileName` immutable
 - by only having `SourceMap::to_real_filename` create `RealFileName`
   - currently `RealFileName` can be created from any `Path` and are remapped afterwards, which creates consistency issue
 - by also making `RealFileName` holds it's working directory, embeddable name and the remapped scopes
   - this removes the need for a `Session`, to know the current(!) scopes and cwd, which is invalid as they may not be equal to the scopes used when creating the filename

In order for `SourceMap::to_real_filename` to know which scopes to apply `FilePathMapping` now takes the current remapping scopes to apply, which makes `FileNameDisplayPreference` and company useless and are removed.

This PR is split-up in multiple commits (unfortunately not atomic), but should help review the changes.

Unblocks rust-lang/rust#147611
Fixes rust-lang/rust#148328

Author: bors

clippy_lints/src/module_style.rs

@@ -81,7 +81,7 @@ pub struct ModStyle {
 
 impl EarlyLintPass for ModStyle {
     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
-        self.working_dir = cx.sess().opts.working_dir.local_path().map(Path::to_path_buf);
+        self.working_dir = cx.sess().source_map().working_dir().local_path().map(Path::to_path_buf);
     }
 
     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {

clippy_utils/src/source.rs

@@ -13,7 +13,7 @@ use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_span::source_map::{SourceMap, original_sp};
 use rustc_span::{
-    BytePos, DUMMY_SP, DesugaringKind, FileNameDisplayPreference, Pos, RelativeBytePos, SourceFile, SourceFileAndLine,
+    BytePos, DUMMY_SP, DesugaringKind, Pos, RelativeBytePos, SourceFile, SourceFileAndLine,
     Span, SpanData, SyntaxContext, hygiene,
 };
 use std::borrow::Cow;
@@ -268,7 +268,7 @@ fn map_range(
         debug_assert!(
             range.start <= text.len() && range.end <= text.len(),
             "Range `{range:?}` is outside the source file (file `{}`, length `{}`)",
-            src.sf.name.display(FileNameDisplayPreference::Local),
+            src.sf.name.prefer_local_unconditionally(),
             text.len(),
         );
         debug_assert!(range.start <= range.end, "Range `{range:?}` has overlapping bounds");