Switch from PurePath#as_uri to PurePath#joinpath

`as_uri` is deprecated in `PurePath`. This commit also introduces a test
to ensure users have a workaround that is not deprecated.

Author: A5rocks

src/trio/_tests/test_path.py

@@ -168,10 +168,14 @@ def test_forward_properties_rewrap(path: trio.Path) -> None:
     assert isinstance(path.parent, trio.Path)
 
 
-async def test_forward_methods_without_rewrap(path: trio.Path) -> None:
+def test_forward_methods_without_rewrap(path: trio.Path) -> None:
+    assert "totally-unique-path" in str(path.joinpath("totally-unique-path"))
+
+
+async def test_path_methods_on_trio_path(path: trio.Path) -> None:
     path = await path.parent.resolve()
 
-    assert path.as_uri().startswith("file:///")
+    assert pathlib.Path.as_uri(path).startswith("file:///")
 
 
 def test_repr() -> None:

src/trio/_tests/type_tests/path.py

@@ -46,7 +46,6 @@ def sync_attrs(path: trio.Path) -> None:
     assert_type(path.suffixes, list[str])
     assert_type(path.stem, str)
     assert_type(path.as_posix(), str)
-    assert_type(path.as_uri(), str)
     assert_type(path.is_absolute(), bool)
     assert_type(path.is_relative_to(path), bool)
     assert_type(path.is_reserved(), bool)