Support ranged media constraints

[at-wat]

Pixel format is scored by complete match at now.
For example, I want to select one of YUY2 and UYVY but not want to use JPEG.

mediadevices/pkg/prop/prop.go

Lines 99 to 112 in 949e850

	// Video represents a video's properties
	type Video struct {
	Width, Height int
	FrameRate float32
	FrameFormat frame.Format
	}
	// Audio represents an audio's properties
	type Audio struct {
	ChannelCount int
	Latency time.Duration
	SampleRate int
	SampleSize int
	}

[at-wat]

https://developer.mozilla.org/en-US/docs/Web/API/Media_Streams_API/Constraints
In WebAPI, constraints can have min, ideal, max, and exact.

For pixel format case, oneof maybe needed as a extension. (or exact: ["YUY2", "UYVY"])

[at-wat]

POC implementation for int propaties: #168
@lherman-cs what do you think about this?

[lherman-cs]

@at-wat I just commented on the PR itself. Overall, it looks really good!