Add RetryCallBack to remote_api.go

[pipiland2612]

Changes

• Add RetryCallBack to remote_api.go to support for providing observability while Write function are being called
• This change is needed because we want to use it in storage/remote/queue_manager.go (prometheus code) see: https://github.com/prometheus/prometheus/blob/a4da440dad4be13da121cce79caa74b1c76ec9f5/storage/remote/queue_manager.go#L1801

[pipiland2612]

cc @bwplotka @saswatamcode

[bwplotka]

Amazing! Thanks.

LGTM, one optional suggestion, but feel free to reject.