typing: set no_implicit_reexport

In Python, if module A defines a name `name`, and module B does `import
name from A`, then another module C can `import name from B`.

Sometimes it is intentional -- module B is meant to "reexport" `name`.
But sometimes it is just confusion/inconsistency on where `name` should
be imported from.

mypy has a flag `--no-implicit-reexport` which puts some order into
this. A name can only be imported from a module if

1. The module defines the name
2. The module's `__all__` includes the name
3. The module imports the name as `from ... import .. as name`.

This flag is included in mypy's `--strict` flag.

I like this flag, but I realize it is a bit controversial, and in
particular item 3 above is a bit unfriendly to contributors who don't
know about it. So I didn't intend to add it to pytest.

But while investigating issue 7589 I came upon mypy issue 8754 which
causes `--no-implicit-reexport` to leak into installed libraries and
causes some unexpected typing differences *in pytest* if the user uses
this flag.

Since the diff mostly makes sense, let's just conform to it.

testing/python/fixtures.py

@@ -3,6 +3,7 @@ import textwrap
 
 import pytest
 from _pytest import fixtures
+from _pytest.compat import getfuncargnames
 from _pytest.config import ExitCode
 from _pytest.fixtures import FixtureRequest
 from _pytest.pathlib import Path
@@ -15,22 +16,22 @@ def test_getfuncargnames_functions():
     def f():
         raise NotImplementedError()
 
-    assert not fixtures.getfuncargnames(f)
+    assert not getfuncargnames(f)
 
     def g(arg):
         raise NotImplementedError()
 
-    assert fixtures.getfuncargnames(g) == ("arg",)
+    assert getfuncargnames(g) == ("arg",)
 
     def h(arg1, arg2="hello"):
         raise NotImplementedError()
 
-    assert fixtures.getfuncargnames(h) == ("arg1",)
+    assert getfuncargnames(h) == ("arg1",)
 
     def j(arg1, arg2, arg3="hello"):
         raise NotImplementedError()
 
-    assert fixtures.getfuncargnames(j) == ("arg1", "arg2")
+    assert getfuncargnames(j) == ("arg1", "arg2")
 
 
 def test_getfuncargnames_methods():
@@ -40,7 +41,7 @@ def test_getfuncargnames_methods():
         def f(self, arg1, arg2="hello"):
             raise NotImplementedError()
 
-    assert fixtures.getfuncargnames(A().f) == ("arg1",)
+    assert getfuncargnames(A().f) == ("arg1",)
 
 
 def test_getfuncargnames_staticmethod():
@@ -51,7 +52,7 @@ def test_getfuncargnames_staticmethod():
         def static(arg1, arg2, x=1):
             raise NotImplementedError()
 
-    assert fixtures.getfuncargnames(A.static, cls=A) == ("arg1", "arg2")
+    assert getfuncargnames(A.static, cls=A) == ("arg1", "arg2")
 
 
 def test_getfuncargnames_partial():
@@ -64,7 +65,7 @@ def test_getfuncargnames_partial():
     class T:
         test_ok = functools.partial(check, i=2)
 
-    values = fixtures.getfuncargnames(T().test_ok, name="test_ok")
+    values = getfuncargnames(T().test_ok, name="test_ok")
     assert values == ("arg1", "arg2")
 
 
@@ -78,7 +79,7 @@ def test_getfuncargnames_staticmethod_partial():
     class T:
         test_ok = staticmethod(functools.partial(check, i=2))
 
-    values = fixtures.getfuncargnames(T().test_ok, name="test_ok")
+    values = getfuncargnames(T().test_ok, name="test_ok")
     assert values == ("arg1", "arg2")