Add user-configurable initial states for DTR and RTS control lines

[guarjo]

Motivation Currently, DTR and RTS are always set to HIGH when opening a serial port. This causes issues with hardware that is sensitive to these control lines (e.g., devices that reset on DTR change, or RS-485 transceivers).

Changes

• Added InitialDTR and InitialRTS boolean properties to TLazSerial
• Modified DeviceOpen() to apply user-specified pin states after configuration
• Changed Config() to use disable flags, preventing automatic pin changes
• Defaults to True for backward compatibility

Testing

• Tested on Windows with COM ports
• Verified no DTR/RTS glitches when InitialDTR/RTS = False
• Confirmed backward compatibility with existing code

Breaking Changes None - defaults preserve original behavior.