Exit quietly on broken pipe in auxiliary output paths

The main output path has exited with status 0 on EPIPE since #232, but
auxiliary outputs still used println!/print!/io::stdout().flush().unwrap()
and panicked (exit code 101) when the reader of a piped stdout went away
early, e.g. 'bat --completion bash | head -n0'.

Route them through the existing convention instead: write!/writeln! to
io::stdout() and '?' so that Error::Io(BrokenPipe) reaches
default_error_handler, which exits with status 0. This covers
--completion, --config-file, --diagnostic (bugreport's print() becomes
format() + writeln!), --generate-config-file, the 'cache' subcommand
progress messages, the OSC title sequence of --set-terminal-title, and
the 'built without feature' notices.

Closes #4034

CHANGELOG.md

@@ -25,6 +25,7 @@
 - Syntax highlighting for Python files using uv as script runner in shebang #3689 (@janlarres)
 
 ## Bugfixes
+- Exit quietly with status 0 instead of panicking when stdout is closed early (broken pipe) on auxiliary output paths such as `--completion`, `--config-file`, `--diagnostic`, `--generate-config-file`, `--set-terminal-title` and `cache --build`/`--clear`, matching the main output path since #232. Closes #4034 (@Mathjk)
 - Track strikethrough (SGR 9 / 29) in the ANSI style tracker so it is re-emitted like bold, dim, italic, and underline, and is no longer dropped after the first highlighted token when displaying ANSI input with syntax highlighting, see #4015 (@mikehasa)
 - Allow boolean flags to be given more than once, so that a flag set in the config file can also be passed on the command line without erroring, see #3912 (@logarithmone1128)
 - Use parsed CLI arguments to detect number flags, see #3908 (@cuishuang)