[TIMOB-26599] iOS: Add "allowTranscoding" option to Ti.Media.openPhotoGallery()

*Summary:* When selecting a video from the gallery, iOS will transcode/convert the selected video by default and return the newly formatted video instead. This can cause a very long delay if the video is large. *Solution:* Add an iOS-only "allowTranscoding" option for our Ti.Media.openPhotoGallery() method, when set false, will return the selected video as-is without transcoding it. This will solve the long delay issue.

Ti.Media.openPhotoGallery({
	allowTranscoding: false,
	mediaTypes: [Ti.Media.MEDIA_TYPE_VIDEO],
	success: function(e) {
		// Got it.
	},
});

*Note:* There is no equivalent to this on Android, which always returns a reference to the video as-is. So, this is an iOS only feature. *Native Implementation Details:* Add this code at line 1746. I can provide a PR

if ([TiUtils isIOS11OrGreater]) {
      BOOL disableVideoCompression = [TiUtils boolValue:@"disableVideoCompression" properties:args def:NO];
      if (disableVideoCompression) {
        picker.videoExportPreset = AVAssetExportPresetPassthrough;
      }
    }
    [self displayModalPicker:picker settings:args];