Add support for powerline frequency on gUM MediaTrackSupportedConstraints

[murillo128]

AFAIK there is no way to control the power line frequency of the video capture device to reduce the light flickering.

The idea would be to add a new powerLineFrequency constraint that can take the following values:

• Auto: The power-line frequency is determined automatically by the system.
• Disabled : Power-line frequency control is disabled.
• 50Hz: The power-line frequency is 50 Hz.
• 60Hz: The power-line frequency is 60 Hz.

For ref:
https://learn.microsoft.com/en-us/uwp/api/windows.media.devices.videodevicecontroller.trysetpowerlinefrequency?view=winrt-22621#windows-media-devices-videodevicecontroller-trysetpowerlinefrequency(windows-media-capture-powerlinefrequency)
https://learn.microsoft.com/en-us/uwp/api/windows.media.capture.powerlinefrequency?view=winrt-22621

[fippo]

More ref: https://source.chromium.org/chromium/chromium/src/+/main:media/capture/video_capture_types.h?q=googPowerLineFrequency%20
This used to be a nonstandard constraint in Chrome but that went AWOL