Consider re-exporting all modules in streamly-core via streamly

[harendra-kumar]

See some discussion regarding this in #533.

IIRC the problem is that if we have re-exported a module from streamly then we cannot use it from streamly-core package. GHC does not recognize them as the same module. So to re-export we have to re-export everything including the internal modules, so that we can use streamly as a complete replacement for streamly-core. So one can use either streamly or streamly-core, does not need both of them together.