SoftwareSerial.end() does not stop the timer in half duplex mode.

[ion-popa]

Describe the bug
SoftwareSerial.end() does not stop the timer in half duplex mode. This is an issue when the controller is in sleep mode, as the timer interrupt is triggered continuously.

To Reproduce

void setup()
{
    SoftwareSerial softSer(PA3, PA3);
    softSer.begin(9600);
    softSer.println("Hello, SoftwareSerial!");
    softSer.end();
    HAL_PWR_EnterSLEEPMode(PWR_LOWPOWERREGULATOR_ON, PWR_SLEEPENTRY_WFI);
}

Expected behavior
SoftwareSerial.end() should stop the timer.

Desktop (please complete the following information):

• OS: Windows
• IDE: VS Code with PlatformIO and platform_packages redirecting to latest Arduino_Core_STM32 release
• STM32 core version: 2.12.0
• Upload method: SWD

Board (please complete the following information):

• Name: Custom board based on STM32L443VC

Additional context
Test were made without starting the software serial, and the board stayed in sleep mode, as expected.

[ion-popa]

The timer is stopped only by calling stopListening which will call setSpeed(0), but since the configuration is made in half duplex mode, the object is not active_listener, the setSpeed(0) is skipped.
Added PR