Remove the IO::Scalar clone

I know it was here for 5.6 support, but it is crazy to keep it at this
point. I have no intention of dragging it forward. Most people on 5.6
would be hard pressed to need this version of Test::Builder anyway.
Name this test properly, Provider gets more tests later
Normalize version across all modules
Diag from OK should go to all listeners, it is not TAP exclusive
Tests to be written
Test::Tester2 docs and tests
Docs and cleanup