Agora RTC Objective-C API Reference Refactor

### - a -

- AUDIO_FRAME_POSITION : IAudioFrameObserverBase
- AUDIO_FRAME_TYPE : IAudioFrameObserverBase
- AudioFilterPosition : IAudioTrack

### - b -

- BACKGROUND_BLUR_DEGREE : VirtualBackgroundSource
- BACKGROUND_SOURCE_TYPE : VirtualBackgroundSource

### - c -

- CAMERA_SOURCE : ICameraCapturer
- CAMERA_STATE : ICameraCapturer
- CaptureMode : IScreenCaptureSource

### - e -

- EGL_CONTEXT_TYPE : ExternalVideoFrame
- EXTENSION_TYPE : IExtensionProvider

### - l -

- LIGHTENING_CONTRAST_LEVEL : BeautyOptions , IVideoBeautyFilter::BeautyOptions
- LOW_LIGHT_ENHANCE_LEVEL : LowlightEnhanceOptions
- LOW_LIGHT_ENHANCE_MODE : LowlightEnhanceOptions

### - m -

- MatrixID : ColorSpace
- MAX_METADATA_SIZE_TYPE : IMetadataObserver
- META_INFO_KEY : IVideoFrameMetaInfo
- METADATA_TYPE : IMetadataObserver

### - n -

- NS_DELAY : ILocalUser
- NS_LEVEL : ILocalUser
- NS_MODE : ILocalUser

### - p -

- PrimaryID : ColorSpace
- ProcessMode : IExtensionVideoFilter
- ProcessResult : IExtensionVideoFilter , ILipSyncFilter

### - r -

- RangeID : ColorSpace

### - s -

- SEG_MODEL_TYPE : SegmentationProperty

### - t -

- TransferID : ColorSpace

### - u -

- USER_MEDIA_INFO : ILocalUserObserver

### - v -

- VIDEO_BUFFER_TYPE : ExternalVideoFrame
- VIDEO_DENOISER_LEVEL : VideoDenoiserOptions
- VIDEO_DENOISER_MODE : VideoDenoiserOptions
- VIDEO_FRAME_PROCESS_MODE : IVideoFrameObserver
- VideoBitrateAdjustType : IRtmpLocalUser