Rollup merge of #143661 - Muscraft:other-suggestion-message, r=estebank

chore: Improve how the other suggestions message gets rendered

Note: This change is part of my ongoing work to use `annotate-snippets` as `rustc`'s emitter

This change started as a way to remove some specialty code paths from `annotate-snippets`, by making the "and {} other candidates" message get rendered like a secondary message with no level, but turned into a fix for the message's Unicode output. Before this change, when using the Unicode output, the other suggestions message would get rendered outside of the main suggestion block, making it feel disconnected from what it was referring to. This change makes it so that the message is on the last line of the block, aligning its rendering with other secondary messages, and making it clear what the message is referring to.

Before:
```
error[E0433]: failed to resolve: use of undeclared type `IntoIter`
   ╭▸ $DIR/issue-82956.rs:28:24
   │
LL │         let mut iter = IntoIter::new(self);
   │                        ━━━━━━━━ use of undeclared type `IntoIter`
   ╰╴
help: consider importing one of these structs
   ╭╴
LL + use std::array::IntoIter;
   ├╴
LL + use std::collections::binary_heap::IntoIter;
   ├╴
LL + use std::collections::btree_map::IntoIter;
   ├╴
LL + use std::collections::btree_set::IntoIter;
   ╰╴
     and 9 other candidates
```

After:
```
error[E0433]: failed to resolve: use of undeclared type `IntoIter`
   ╭▸ $DIR/issue-82956.rs:28:24
   │
LL │         let mut iter = IntoIter::new(self);
   │                        ━━━━━━━━ use of undeclared type `IntoIter`
   ╰╴
help: consider importing one of these structs
   ╭╴
LL + use std::array::IntoIter;
   ├╴
LL + use std::collections::binary_heap::IntoIter;
   ├╴
LL + use std::collections::btree_map::IntoIter;
   ├╴
LL + use std::collections::btree_set::IntoIter;
   │
   ╰ and 9 other candidates
```

1 files changed, 7 insertions, 2 deletions

diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 510f37f37e2..95400ac2ca3 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -2446,17 +2446,22 @@ impl HumanEmitter {
                     | DisplaySuggestion::Underline => row_num - 1,
                     DisplaySuggestion::None => row_num,
                 };
-                self.draw_col_separator_end(&mut buffer, row, max_line_num_len + 1);
+                if other_suggestions > 0 {
+                    self.draw_col_separator_no_space(&mut buffer, row, max_line_num_len + 1);
+                } else {
+                    self.draw_col_separator_end(&mut buffer, row, max_line_num_len + 1);
+                }
                 row_num = row + 1;
             }
         }
         if other_suggestions > 0 {
+            self.draw_note_separator(&mut buffer, row_num, max_line_num_len + 1, false);
             let msg = format!(
                 "and {} other candidate{}",
                 other_suggestions,
                 pluralize!(other_suggestions)
             );
-            buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
+            buffer.append(row_num, &msg, Style::NoStyle);
         }
 
         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;