- move the Py_Main documentation from the very high level API section
  to the initialization and finalization section
- make it clear that it encapsulates a full Py_Initialize/Finalize
  cycle of its own
- point out that exactly which settings will be read and applied
  correctly when called after a separate Py_Initialize or
  Py_InitalizeEx call is version dependent
- be explicit that Py_IsInitialized can be called prior to
  initialization
- actually test that Py_IsInitialized can be called prior to
  initialization

- also check Py_IsInitialized while the interpreter is initialized
  and after it is finalized
- flush stdout in the embedding tests that run code so it appears
  in the expected order when running with "-vv"
- make "-vv" on the subinterpreter embedding tests less spammy

…fter-py-initialize

…tion

…er-py-initialize

Co-authored-by: Carol Willing <carolcode@willingconsulting.com>