new_interpreter() now calls _PyBuiltin_Init() to create the builtins
module and calls _PyImport_FixupBuiltin(), rather than using
_PyImport_FindBuiltin(tstate, "builtins").

pycore_init_builtins() is now responsible to initialize
intepr->builtins_copy: inline _PyImport_Init() and remove this
function.

If _PyImport_FixupExtensionObject() is called from a subinterpreter,
leave extensions unchanged and don't copy the module dictionary
into def->m_base.m_copy.

* Add GCState type for readability
* gcmodule.c now gets its gcstate from tstate
* _PyGC_DumpShutdownStats() now expects tstate rather than runtime
* Rename "state" to "gcstate" for readability: to avoid confusion
  between "state" and "tstate" for example.
* collect() now only expects tstate: it gets gcstate from tstate.
* Pass tstate to _PyErr_xxx() functions

Use forward declaration of types to avoid includes in the internal C
API. Add also comment to justify other includes.

Relative imports use resolve_name to get the absolute target name,
which first seeks the current module's absolute package name from the globals:
If __package__ (and __spec__.parent) are missing then
import uses __name__, truncating the last segment if
the module is a submodule rather than a package __init__.py
(which it guesses from whether __path__ is defined).

The __name__ attempt should fail if there is no parent package (top level modules),
if __name__ is '__main__' (-m entry points), or both (scripts).
That is, if both __name__ has no subcomponents and the module does not seem
to be a package __init__ module then import should fail.

Imports now raise `TypeError` instead of `ValueError` for relative import failures. This makes things consistent between `builtins.__import__` and `importlib.__import__` as well as using a more natural import for the failure.


https://bugs.python.org/issue37444



Automerge-Triggered-By: @brettcannon

* Fix typos in comments, docs and test names

* Update test_pyparse.py

account for change in string length

* Apply suggestion: splitable -> splittable

Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Apply suggestion: splitable -> splittable

Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Apply suggestion: Dealloccte -> Deallocate

Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Update posixmodule checksum.

* Reverse idlelib changes.