Added logic to retry transient failures for all operations in desktop storage implementation. (#824)

* Update GetBytes to repreatedly sent requests until one succeeds

* Generalized retry logic, added retry to GetFile, added exponential backoff, no longer cancel once deadline is reached, just don't retry after this point. Added integration test that retries 404 errors.

* some minor cleanup - removed temporary debug logs in the integration test, defined constants for initial and max sleep time

* Make changes based on review feedback

* Changes based on review feedback

* Add retry logic to all operations in desktop storage implementation, not just get bytes

* Only extern g_retry_file_not_found_for_testing in FIREBASE_PLATFORM_DESKTOP version of integration tests

* Add integration tests to retry GetBytes, GetFile, GetMetadata, and Delete

* Add integration test to retry PutFile by having nonexistent local file

* Update release notes

* single variable to retry all errors and other minor review feedback

* Remove unused include

Author: AlmostMatt

release_build_files/readme.md

@@ -573,6 +573,7 @@ code.
         initialization of Firebase iOS SDK.
     -   Remote Config: Fixed default `Fetch()` timeout being 1000 times too
         high.
+    -   Storage (Desktop): Added retry logic to PutFile, GetFile, and other operations.
 
 ### 8.9.0
 -   Changes