Add unicode coercion of logged messages to ContextFormatter

The ContextAdapter is being retired as part of
blueprint remove-context-adapter so any processing in the
ContextAdapter needs to be added to the ContextFormatter.

Coercion in the ContextAdapter was fixed as part
of change-id: I26b0d3490f731f6fdb9a429aa9ef59360ddc88ba

Partially implements blueprint remove-context-adapter

Change-Id: Icf4533074b45623983f4e3eeb7e1a1ae618bf605
Merge "Add unicode coercion of logged messages to ContextFormatter"