[react-native] Memory leak when programmatically changing 'source' prop of Image

[https://github.com/facebook/react-native/issues/12220](https://github.com/facebook/react-native/issues/12220)

Start by reading the linked React Native issue #12220, since this board entry provides no files, tests, or reproduction details. Identify the affected Image source update path and any referenced diagnostics there; done means the reported memory leak is fixed and the relevant behavior is covered by the project's validation.

索引モデルが issue の本文から書いたものです。