Auto merge of #117507 - nnethercote:rustc_span, r=Nilstrieb

`rustc_span` cleanups

Just some things I found while looking over this crate.

r? `@oli-obk`

src/diagnostics.rs

@@ -4,7 +4,7 @@ use std::num::NonZeroU64;
 use log::trace;
 
 use rustc_errors::DiagnosticMessage;
-use rustc_span::{source_map::DUMMY_SP, SpanData, Symbol};
+use rustc_span::{DUMMY_SP, SpanData, Symbol};
 use rustc_target::abi::{Align, Size};
 
 use crate::borrow_tracker::stacked_borrows::diagnostics::TagHistory;

src/eval.rs

@@ -267,7 +267,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
     let layout_cx = LayoutCx { tcx, param_env };
     let mut ecx = InterpCx::new(
         tcx,
-        rustc_span::source_map::DUMMY_SP,
+        rustc_span::DUMMY_SP,
         param_env,
         MiriMachine::new(config, layout_cx),
     );