treewide: replace lock_guard with scoped_lock

SonarLint reports the latter to be better:

std::scoped_lock basically provides the same feature as std::lock_guard,
but is more generic: It can lock several mutexes at the same time, with a
deadlock prevention mechanism (see {rule:cpp:S5524}). The equivalent code
to perform simultaneous locking with std::lock_guard is significantly more
complex. Therefore, it is simpler to use std::scoped_lock all the time,
even when locking only one mutex (there will be no performance impact).

Signed-off-by: Rosen Penev <rosenp@gmail.com>

test/dump_text_file.cxx

@@ -68,7 +68,7 @@ dump_input_stream(InputStreamPtr &&is)
 		dump_text_file(tis);
 	}
 
-	const std::lock_guard<Mutex> protect(is->mutex);
+	const std::scoped_lock<Mutex> protect(is->mutex);
 
 	is->Check();
 	return 0;