refactor(venv): Move py_venv template files into a dedicated templates/ subdirectory (#1310)

This change reorganizes the `py_venv` template files by moving
`_virtualenv.py`, `link.py`, `venv.tmpl.sh`, and `venv_activate.tmpl.sh`
into a new templates/ subdirectory under py/private/py_venv. It also
updates the corresponding Bazel references and test imports so
everything still resolves correctly.

---

### Changes are visible to end-users: no

### Test plan

- Covered by existing test cases

Author: xangcastle

py/private/py_venv/BUILD.bazel

@@ -4,10 +4,10 @@ load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")
 package(default_visibility = ["//py:__subpackages__"])
 
 exports_files([
-    "_virtualenv.py",
-    "link.py",
-    "venv.tmpl.sh",
-    "venv_activate.tmpl.sh",
+    "templates/_virtualenv.py",
+    "templates/link.py",
+    "templates/venv.tmpl.sh",
+    "templates/venv_activate.tmpl.sh",
 ])
 
 bool_flag(

py/private/py_venv/py_venv.bzl

@@ -225,11 +225,11 @@ does not reinsert a wheel.
     # Shared with py_binary via the venv-assembly helper.
     "_venv_activate_tmpl": attr.label(
         allow_single_file = True,
-        default = ":venv_activate.tmpl.sh",
+        default = "//py/private/py_venv:templates/venv_activate.tmpl.sh",
     ),
     "_virtualenv_shim": attr.label(
         allow_single_file = True,
-        default = ":_virtualenv.py",
+        default = "//py/private/py_venv:templates/_virtualenv.py",
     ),
     "_windows_constraint": attr.label(
         default = "@platforms//os:windows",
@@ -270,7 +270,7 @@ environment. Forwarded to the sibling py_binary/py_test consumer
     ),
     "_run_tmpl": attr.label(
         allow_single_file = True,
-        default = ":venv.tmpl.sh",
+        default = "//py/private/py_venv:templates/venv.tmpl.sh",
     ),
 })
 
@@ -476,7 +476,7 @@ def py_venv_link(name, venv, link_name = None, **kwargs):
             target's package + venv name.
         **kwargs: Forwarded to the underlying `py_binary`.
     """
-    link_script = str(Label(":link.py"))
+    link_script = str(Label("//py/private/py_venv:templates/link.py"))
     _py_venv_exec(
         name = name,
         main = link_script,

py/private/py_venv/_virtualenv.py …private/py_venv/templates/_virtualenv.pypy/private/py_venv/_virtualenv.py renamed to py/private/py_venv/templates/_virtualenv.py py/private/py_venv/_virtualenv.py renamed to py/private/py_venv/templates/_virtualenv.py

@@ -65,9 +65,9 @@ write_source_files(
 py_test(
     name = "test_link",
     srcs = [
-        "//py/private/py_venv:link.py",
+        "//py/private/py_venv:templates/link.py",
         "//py/private/py_venv/tests:test_link.py",
     ],
-    imports = [".."],
+    imports = ["../templates"],
     main = "//py/private/py_venv/tests:test_link.py",
 )