Propagate client-side cancellations to the caller

[dzmitry-tsarevich]

First, thank you for great cache package.
Second, caching course is very nice!

We use your package in production environment a lot, and facing some problems with client-side cancellations.
When client cancels request, package spams TaskCancelledException to error log:

FUSION [N="XXXX" I="0HNO4IRJRGTJL"] (O="0HNO4IRK6U06C" K="YYYY"): [DC] an error occurred while deserializing an entry

What's bad is log also has exception stack trace so it reduces our servers performance for no reason.
Also as activity marked as error and TaskCancelledException exception is saved in, we have unneeded spam in traces.

• Fixes logs spam due to TaskCancelledException writes.
• Speedups cancellations processing as no logs means no exception stack traces which are slow to build.
• Do not pollute activities with TaskCancelledExceptions.
• Fixes propagation of client-side cancellations in ex. web API requests.