Android: Support HTTP headers for source prop on <Image> components

Summary:
A copy of https://github.com/facebook/react-native/pull/7791 because of our very imperfect tools that mirror the changes from pull requests in the fb monorepo. The internal Phabricator revision for #7791 is in an 'abandoned' state (by foghina probably because of changing teams) and Phabricator doesn't allow me to claim that revision and merge it. Therefore I'm creating a new one.

(It's not foghina's fault, no one probably knew about this "abandoned Phabricator revision" edge case, don't remember we hit it before.)

Will try to keep attribution (git blame) to rigdern when merging.
Closes https://github.com/facebook/react-native/pull/12448

Differential Revision: D4584743

Pulled By: mkonicek

fbshipit-source-id: 66e5b88134fca1980adc4cd8a2ff17c42e10022c