Protostellar: Expose KV operation option values publicly.

The protostellar wrappers need the values in the various KV operations (e.g. GetOptions, UpsertOptions, etc.) that are currently internal.

Possible solution to fix two issues at the same time:  Create a readonly record equivalent for each KV options type, then use those values instead of the internal fields on the options types.  This eliminates the potential race condition on users re-using an UpsertOptions instance and changing values while an operation is running.