For customizing back button image we use platform native functionality that is: `setBackIndicatorImage` on iOS and `setHomeAsUpIndicator` on Android.
The reason we don't do that just by setting left item is that we get a couple of things for free such as handling RTL properly, working accessibility features, handling prop for hiding back button and a couple more.
Unfortunately there are some downsides to that approach too. We need to install the back button as an Image component from the JS side, and the extract the image payload on the native side to set it with the navigator. This is specifically problematic in DEV mode where images are loaded asynchronously over HTTP from the packager. In order for that to work we had to employ a few hacks (more comments on that in the code).
When some of config props change or new header items are added we need to perform a header update. This diff adds logic to trigger updating header props when that happens.
This change fixes the problem when header would update to the previous screen configuration as a result of starting swipe back gesture but never restore to the original one in case swipe back gets cancelled (e.g. user didn't swipe far enough). The problem was that as a result of swipe back we'd apply header config changes but after cancel there was no trigger to reset header to the previous state.
