Replace std::lock_guard and std::lock with std::scoped_lock (#1758)

std::scoped_lock was introduced in C++17 and is strictly better than
std::lock_guard as it supports locking any number of mutexes safely.
It's also easier to use than std::lock for locking multiple mutexes at
once.

wpilibc/src/main/native/cpp/MotorSafety.cpp

@@ -23,12 +23,12 @@ static wpi::SmallPtrSet<MotorSafety*, 32> instanceList;
 static wpi::mutex listMutex;
 
 MotorSafety::MotorSafety() {
-  std::lock_guard lock(listMutex);
+  std::scoped_lock lock(listMutex);
   instanceList.insert(this);
 }
 
 MotorSafety::~MotorSafety() {
-  std::lock_guard lock(listMutex);
+  std::scoped_lock lock(listMutex);
   instanceList.erase(this);
 }
 
@@ -51,32 +51,32 @@ MotorSafety& MotorSafety::operator=(MotorSafety&& rhs) {
 }
 
 void MotorSafety::Feed() {
-  std::lock_guard lock(m_thisMutex);
+  std::scoped_lock lock(m_thisMutex);
   m_stopTime = Timer::GetFPGATimestamp() + m_expiration;
 }
 
 void MotorSafety::SetExpiration(double expirationTime) {
-  std::lock_guard lock(m_thisMutex);
+  std::scoped_lock lock(m_thisMutex);
   m_expiration = expirationTime;
 }
 
 double MotorSafety::GetExpiration() const {
-  std::lock_guard lock(m_thisMutex);
+  std::scoped_lock lock(m_thisMutex);
   return m_expiration;
 }
 
 bool MotorSafety::IsAlive() const {
-  std::lock_guard lock(m_thisMutex);
+  std::scoped_lock lock(m_thisMutex);
   return !m_enabled || m_stopTime > Timer::GetFPGATimestamp();
 }
 
 void MotorSafety::SetSafetyEnabled(bool enabled) {
-  std::lock_guard lock(m_thisMutex);
+  std::scoped_lock lock(m_thisMutex);
   m_enabled = enabled;
 }
 
 bool MotorSafety::IsSafetyEnabled() const {
-  std::lock_guard lock(m_thisMutex);
+  std::scoped_lock lock(m_thisMutex);
   return m_enabled;
 }
 
@@ -85,7 +85,7 @@ void MotorSafety::Check() {
   double stopTime;
 
   {
-    std::lock_guard lock(m_thisMutex);
+    std::scoped_lock lock(m_thisMutex);
     enabled = m_enabled;
     stopTime = m_stopTime;
   }
@@ -106,7 +106,7 @@ void MotorSafety::Check() {
 }
 
 void MotorSafety::CheckMotors() {
-  std::lock_guard lock(listMutex);
+  std::scoped_lock lock(listMutex);
   for (auto elem : instanceList) {
     elem->Check();
   }