clean UploadFileOperation.java

Description

While testing epic branch, I encounter many issue with Upload Operation. so this MR fix one issue:

• No Context where passed to it

but also fix coding style, variable naming convention, etc.

I also remove the implementation of Parcelable interface because it was previously used to pass this instance from ObserverService to SynchronizationService. But UploadFileOperation instance are now instanciated directly into SynchronizationService.

Check list

• Self review
• code review