Minimize pub usage in source_map.rs.

Most notably, this commit changes the `pub use crate::*;` in that file
to `use crate::*;`. This requires a lot of `use` items in other crates
to be adjusted, because everything defined within `rustc_span::*` was
also available via `rustc_span::source_map::*`, which is bizarre.

The commit also removes `SourceMap::span_to_relative_line_string`, which
is unused.

Author: nnethercote

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),
     );