[upstream_utils] Rename expected's detail namespace to detail_expected (#7048)

Previously, both wpi/expected and JSON's cpp_future.h would define enable_if_t and conjunction in wpi::detail, leading to conflicts if both were included in the same cpp source file. By renaming the namespace wpi/expected uses, there is no longer a conflict.

upstream_utils/expected.py

@@ -15,12 +15,14 @@ def copy_upstream_src(wpilib_root):
     )
     shutil.copyfile("include/tl/expected.hpp", dest_filename)
 
-    # Rename namespace from tl to wpi
+    # Rename namespace from tl to wpi, and detail to detail_expected
     with open(dest_filename) as f:
         content = f.read()
     content = content.replace("namespace tl", "namespace wpi")
     content = content.replace("tl::", "wpi::")
     content = content.replace("TL_", "WPI_")
+    content = content.replace("namespace detail", "namespace detail_expected")
+    content = content.replace("detail::", "detail_expected::")
     with open(dest_filename, "w") as f:
         f.write(content)