1. Implement all read() primitives using readLoop() like it was done in streams.
2. Fix readLine() bug.
3. Add readMessage() primitive.
4. Fixing exception hierarchy, handling code and simplification of (break/continue + exception).
5. Fix TLSStream closure procedure.
6. Add BoundedStream stream and tests.
7. Remove `result` usage from the code.
This reverts commit d0a17d551f.
Moving CancelledError outside of the established Nim hierarchy is
not a solution that has rough consensus and has an unknown impact
on compatibility with otherwise correctly implemented cancellation
code (for example when `CatchableError` is caught, cleanup is done,
then the exception is reraised). Further, this breaks the established
convention in the Nim community that Exception should not be inherited
from, complicating compatibility with future Nim versions that may
enforce this more strongly.