[native] Rename callbacks in InputStateContainer:uploadFile for clarity

Summary:
The fail(...) and finish(...) naming was confusing both when defined and at callsites.

I think switching the naming to onUpload[Finished/Failed] makes things clearer.

Test Plan: This is a noop, no functional change.

Reviewers: abosh, varun, tomek, jacek

Reviewed By: abosh

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D4900