setup test to use custom queue for RCTImageStoreManager operations instead of module queue (#41178)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/41178

Changelog: [Internal]

in my quest to get rid of all synthesized `methodQueue`s, we have `RCTImageStoreManager` which uses this throughout. in this diff, i add a config that uses a queue that is managed by the module itself instead of the one generated by the infra.

Reviewed By: cipolleschi

Differential Revision: D50585904

fbshipit-source-id: a33f8a4844fe3ef861bf1c3a7b87a9ed4b24d13f