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/RemoteTagCache.cxx

@@ -98,7 +98,7 @@ RemoteTagCache::ItemResolved(Item &item) noexcept
 void
 RemoteTagCache::InvokeHandlers() noexcept
 {
-	const std::lock_guard<Mutex> lock(mutex);
+	const std::scoped_lock<Mutex> lock(mutex);
 
 	while (!invoke_list.empty()) {
 		auto &item = invoke_list.front();
@@ -125,7 +125,7 @@ RemoteTagCache::Item::OnRemoteTag(Tag &&_tag) noexcept
 
 	scanner.reset();
 
-	const std::lock_guard<Mutex> lock(parent.mutex);
+	const std::scoped_lock<Mutex> lock(parent.mutex);
 	parent.ItemResolved(*this);
 }
 
@@ -137,6 +137,6 @@ RemoteTagCache::Item::OnRemoteTagError(std::exception_ptr e) noexcept
 
 	scanner.reset();
 
-	const std::lock_guard<Mutex> lock(parent.mutex);
+	const std::scoped_lock<Mutex> lock(parent.mutex);
 	parent.ItemResolved(*this);
 }