Fixes#4288.
- Default imports to THIRD_PARTY, so in effect we merge the FIRST_PARTY and THIRD_PARTY stubs. This means import order is no longer affected by whether typing_extensions is installed locally.
- Treat typing_extensions, _typeshed and some others as standard library modules.
Note that isort master is very different from the latest release; we'll have to do something
different if and when the next isort release comes out.
* Fix incorrect usage of AnyStr
- sqlite3 was using Union[bytes, AnyStr], which doesn't make sense
- The urllib functions I changed accept either bytes or str for their "safe"
argument
- Also added supports for PathLike to pstats
- Remove some unused imports of AnyStr
* pstats: python 2 accepts unicode
