Vulkan: pipeline cache not populated as blob cache is not set 1. Use vkMergePipelineCaches in eglSetBlobCacheFuncsANDROID as blob cache callbacks are set after eglInititalize. 2. Use a more proper way to save the cache data to disk. Bug: angleproject:3318 Change-Id: Ieb5d10ab93e7afb2aab4446b387d7f36c878a686 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1559671 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>