fix: improve ParseDiagnostic display format

[bartlomieju]

Summary

• Add SyntaxError: prefix to ParseDiagnostic::Display output
• Show line numbers with pipe margins and move location after the snippet
• Refactor get_range_text_highlight into get_range_highlight_entries returning structured HighlightEntry data instead of a plain string

Before:

Expression expected at file:///my_file.ts:1:22

  setTimeout(() => {}),
                       ~

After:

SyntaxError: Expression expected
  |
1 | setTimeout(() => {}),
  |                      ~
    at file:///my_file.ts:1:22

Context

This was requested as part of denoland/deno_graph#637 (review) — the formatting logic belongs in deno_ast rather than being done by parsing the display string in deno_graph.