Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/unittest/main.pyi

@@ -0,0 +1,49 @@
+import sys
+import unittest.case
+import unittest.loader
+import unittest.result
+import unittest.suite
+from types import ModuleType
+from typing import Any, Iterable, List, Optional, Protocol, Type, Union
+
+class _TestRunner(Protocol):
+    def run(self, test: Union[unittest.suite.TestSuite, unittest.case.TestCase]) -> unittest.result.TestResult: ...
+
+# not really documented
+class TestProgram:
+    result: unittest.result.TestResult
+    module: Union[None, str, ModuleType]
+    verbosity: int
+    failfast: Optional[bool]
+    catchbreak: Optional[bool]
+    buffer: Optional[bool]
+    progName: Optional[str]
+    warnings: Optional[str]
+
+    if sys.version_info >= (3, 7):
+        testNamePatterns: Optional[List[str]]
+    def __init__(
+        self,
+        module: Union[None, str, ModuleType] = ...,
+        defaultTest: Union[str, Iterable[str], None] = ...,
+        argv: Optional[List[str]] = ...,
+        testRunner: Union[Type[_TestRunner], _TestRunner, None] = ...,
+        testLoader: unittest.loader.TestLoader = ...,
+        exit: bool = ...,
+        verbosity: int = ...,
+        failfast: Optional[bool] = ...,
+        catchbreak: Optional[bool] = ...,
+        buffer: Optional[bool] = ...,
+        warnings: Optional[str] = ...,
+        *,
+        tb_locals: bool = ...,
+    ) -> None: ...
+    def usageExit(self, msg: Any = ...) -> None: ...
+    def parseArgs(self, argv: List[str]) -> None: ...
+    if sys.version_info >= (3, 7):
+        def createTests(self, from_discovery: bool = ..., Loader: Optional[unittest.loader.TestLoader] = ...) -> None: ...
+    else:
+        def createTests(self) -> None: ...
+    def runTests(self) -> None: ...  # undocumented
+
+main = TestProgram