Timer: add hasElapsed, advanceIfElapsed (#2322)

The current hasPeriodPassed() function is confusing.  In preparation for deprecating it,
add new advanceIfElapsed() function with same functionality and hasElapsed() function
which only checks that the time period has elapsed and does not advance the timer.

Also fix a couple of incorrect usages of hasPeriodPassed().

wpilibNewCommands/src/main/native/cpp/frc2/command/RamseteCommand.cpp

@@ -138,5 +138,5 @@ void RamseteCommand::Execute() {
 void RamseteCommand::End(bool interrupted) { m_timer.Stop(); }
 
 bool RamseteCommand::IsFinished() {
-  return m_timer.HasPeriodPassed(m_trajectory.TotalTime());
+  return m_timer.HasElapsed(m_trajectory.TotalTime());
 }