Be more accurate about calculating `display_col` from a `BytePos`

No longer track "zero-width" chars in `SourceMap`, read directly from the line when calculating the `display_col` of a `BytePos`. Move `char_width` to `rustc_span` and use it from the emitter.

This change allows the following to properly align in terminals (depending on the font, the replaced control codepoints are rendered as 1 or 2 width, on my terminal they are rendered as 1, on VSCode text they are rendered as 2):

```
error: this file contains an unclosed delimiter
  --> $DIR/issue-68629.rs:5:17
   |
LL | ␜␟ts␀![{i
   |       -- unclosed delimiter
   |       |
   |       unclosed delimiter
LL | ␀␀  fn rݻoa>rݻm
   |                ^
```

1 files changed, 0 insertions, 6 deletions

diff --git a/compiler/rustc_query_system/src/ich/impls_syntax.rs b/compiler/rustc_query_system/src/ich/impls_syntax.rs
index 5bd4fe04848..39da5e395c4 100644
--- a/compiler/rustc_query_system/src/ich/impls_syntax.rs
+++ b/compiler/rustc_query_system/src/ich/impls_syntax.rs
@@ -73,7 +73,6 @@ impl<'a> HashStable<StableHashingContext<'a>> for SourceFile {
             source_len: _,
             lines: _,
             ref multibyte_chars,
-            ref non_narrow_chars,
             ref normalized_pos,
         } = *self;
 
@@ -98,11 +97,6 @@ impl<'a> HashStable<StableHashingContext<'a>> for SourceFile {
             char_pos.hash_stable(hcx, hasher);
         }
 
-        non_narrow_chars.len().hash_stable(hcx, hasher);
-        for &char_pos in non_narrow_chars.iter() {
-            char_pos.hash_stable(hcx, hasher);
-        }
-
         normalized_pos.len().hash_stable(hcx, hasher);
         for &char_pos in normalized_pos.iter() {
             char_pos.hash_stable(hcx, hasher);