Additions to the Serial UART API (#22953)

- Added an empty constructor, setPort, and validatePort functions for Serial API
- Changed GPS to not allocate Serial object dynamically
- Moved access check on serial port name into the Serial API
- Improved the Qurt platform validatePort Serial function to implement a more rigorous check. Added safety check
to the setPort Serial function to make sure it isn't called after the port has been already opened.

platforms/common/Serial.cpp

@@ -36,6 +36,10 @@
 namespace device
 {
 
+Serial::Serial() :
+	_impl(nullptr, 57600, ByteSize::EightBits, Parity::None, StopBits::One, FlowControl::Disabled) {}
+
+
 Serial::Serial(const char *port, uint32_t baudrate, ByteSize bytesize, Parity parity, StopBits stopbits,
 	       FlowControl flowcontrol) :
 	_impl(port, baudrate, bytesize, parity, stopbits, flowcontrol)
@@ -135,4 +139,14 @@ const char *Serial::getPort() const
 	return _impl.getPort();
 }
 
+bool Serial::validatePort(const char *port)
+{
+	return SerialImpl::validatePort(port);
+}
+
+bool Serial::setPort(const char *port)
+{
+	return _impl.setPort(port);
+}
+
 } // namespace device