[3.12] gh-108303: Move double_const to test_import where it belongs (GH-112108) (#112976)

gh-108303: Move `double_const` to `test_import` where it belongs (GH-112108)
(cherry picked from commit 0738b9a)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>

Author: miss-islington

Lib/test/test_import/__init__.py

@@ -406,9 +406,12 @@ def test_case_sensitivity(self):
             import RAnDoM
 
     def test_double_const(self):
-        # Another brief digression to test the accuracy of manifest float
-        # constants.
-        from test import double_const  # don't blink -- that *was* the test
+        # Importing double_const checks that float constants
+        # serialiazed by marshal as PYC files don't lose precision
+        # (SF bug 422177).
+        from test.test_import.data import double_const
+        unload('test.test_import.data.double_const')
+        from test.test_import.data import double_const
 
     def test_import(self):
         def test_with_extension(ext):