Store all backend_parameters

[MattMcL4475]

Problem:
The current spec says: "Backends shall not store or return unsupported keys if included in a task."

However, we need to store these arbitrary keys from Cromwell so that we can do reporting with them.

Solution:
Store all backend_parameters

Describe alternatives you've considered
Adding a config setting for it, but it's unlikely anyone would know or want to turn off storing these.

[BMurri]

According to the cromwell code that populates the submitted tesTask objects (their develop branch at the current time) they are only writing two backend_parameters but a bunch of tags, which appears to be the place they may be dumping the "labels" which IIRC are the things we wanted them to pipe to us from the options file.