chore: use lazy imports for concurrent.futures

This module has a manual lazy import hack using `__getattr__`. Now that lazy imports exist and cannot be disabled, this could use lazy imports instead.

Key differences: this will now show up in sys.lazy_modules when accessed. Error messages should be a bit better without the wrapper `__getattr__` involved.  That's the only differences I can think of.

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

Author: henryiii

Lib/concurrent/futures/__init__.py

@@ -17,6 +17,9 @@
                                       wait,
                                       as_completed)
 
+lazy from .process import ProcessPoolExecutor
+lazy from .thread import ThreadPoolExecutor
+
 __all__ = [
     'FIRST_COMPLETED',
     'FIRST_EXCEPTION',
@@ -40,26 +43,10 @@
     _interpreters = None
 
 if _interpreters:
+    lazy from .interpreter import InterpreterPoolExecutor
     __all__.append('InterpreterPoolExecutor')
 
 
 def __dir__():
     return __all__ + ['__author__', '__doc__']
 
-
-def __getattr__(name):
-    global ProcessPoolExecutor, ThreadPoolExecutor, InterpreterPoolExecutor
-
-    if name == 'ProcessPoolExecutor':
-        from .process import ProcessPoolExecutor
-        return ProcessPoolExecutor
-
-    if name == 'ThreadPoolExecutor':
-        from .thread import ThreadPoolExecutor
-        return ThreadPoolExecutor
-
-    if _interpreters and name == 'InterpreterPoolExecutor':
-        from .interpreter import InterpreterPoolExecutor
-        return InterpreterPoolExecutor
-
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")