Immutable Classes for Cache

[briansain]

Hi, we're building services that use the new HybridCache with a redis backend. One of the limitations is deserialization takes place for every get request, even for the IMemoryCache in process store. This is a design choice of the library and can be avoided by adding an attribute to the class.

I think it would be beneficial to have an immutable version of the different resource classes so that cache look ups are optimized and CPU overhead is reduced.