Added access to the coroutine context from within any function call.

[accelerated]

Signed-off-by: Alexander Damian adamian@bloomberg.net

Describe your changes

• Add access to the coroutine context from within any function. This allows to yield, sleep or call any ICoroContext API (such as creating new coroutines) if the function is invoked from a coroutine.
• changed inner namespace quantum::cls to quantum::local.
• Added GenericFuture class. This facade util class can wrap any future type at runtime, when the execution context is unknown and can be determined via quantum::local::context();
  Example:

//We want to post a coroutine but this API can be called from either a regular 
//thread or a coroutine. Since we can't block inside a coroutine, the future 
//returned must be 'smart' and block only if in a thread.
GenericFuture<int> someApi(...)
{
    ... //business logic
    auto ctx = local::context(); //get coroutine context if any
    if (ctx) {
        //post via coroutine context
        return {ctx->post(...), ctx}; 
    }
    else {
        //post via dispatcher
        return dispatcher->post(...);
    }
}

// usage will be:
int i = someApi(...).get(); //if we are inside a coroutine we won't block but yield instead

Testing performed
Created specific GTEST for this scenario.

[accelerated]

@demin80 can you please take a look?

[demin80]

looks good to me