[TIMOB-20397] iOS: Main-Thread: Proxies become nil if not created with pageContext

This issue occurs in several cases when we want to use a proxy (like TiBlob and TiUILivePhoto) and running on main-thread. The usual warning is \[WARN\] Creating \[object TiBlob\] in a different context than the calling function.. Example:

Ti.Media.openPhotoGallery({
    mediaTypes: [Ti.Media.MEDIA_TYPE_PHOTO],
    success: function(e) {
      Ti.API.warn(e.mediaType);
      Ti.API.warn(e.media);
    }
  });

var win = Ti.UI.createWindow({backgroundColor: "#fff"});
win.open();

It is caused because we create a blob using TiBlob *media = \[\[\[TiBlob alloc\] initWithImage:resultImage\]\]; instead of using the page context:

TiBlob *media = [[[TiBlob alloc\] _initWithPageContext:[self pageContext]] autorelease];
[media setImage:resultImage];

This issue effects TIMOB-19666 and possibly many other proxies that have not been tested, yet. We need to make sure that the proxies are created properly and write unit tests to ensure their integrity.