Add ability to have different default data exchange mimetypes

[colombod]

When sharing values we need to be able to get data from kernels like T-SQL / SQL / KQB / DuckDB the default mimetype to use should be using other than application/json to support automatic translation to Panda Data.

In general each kernel should be able to override the default mime type to use during data exchange and advertise it via the KernelInfo to enable content negotiation strategies.