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>

src/input/InputStream.cxx

@@ -97,7 +97,7 @@ InputStream::ReadTag() noexcept
 std::unique_ptr<Tag>
 InputStream::LockReadTag() noexcept
 {
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 	return ReadTag();
 }
 
@@ -152,7 +152,7 @@ InputStream::LockReadFull(void *ptr, size_t _size)
 bool
 InputStream::LockIsEOF() const noexcept
 {
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 	return IsEOF();
 }