feat: Have pip_compile generate a *.test target; deprecate *_test (bazel-contrib#2812)

Fixes bazel-contrib#2794.

The `pip_compile` macro generates `*_test` and `*.update` targets. This
pattern does not match with other macros that generate similar targets,
namely `gazelle_python_manifest` and uv `lock` (though that's `.run`
instead of `.test` but either way, it uses a dot `.` instead of
underscore
`_`).

Adjust the macro so that a `.test` target is made. The `_test` target is
aliased with a deprecation warning, to be removed in the next major
version.

Author: dougthor42

CHANGELOG.md

@@ -57,6 +57,9 @@ END_UNRELEASED_TEMPLATE
 * (rules) On Windows, {obj}`--bootstrap_impl=system_python` is forced. This
   allows setting `--bootstrap_impl=script` in bazelrc for mixed-platform
   environments.
+* (rules) {obj}`pip_compile` now generates a `.test` target. The `_test` target is deprecated
+  and will be removed in the next major release.
+  ([#2794](https://github.com/bazel-contrib/rules_python/issues/2794)
 
 {#v0-0-0-fixed}
 ### Fixed

python/private/pypi/pip_compile.bzl

@@ -47,7 +47,7 @@ def pip_compile(
 
     It also generates two targets for running pip-compile:
 
-    - validate with `bazel test [name]_test`
+    - validate with `bazel test [name].test`
     - update with   `bazel run [name].update`
 
     If you are using a version control system, the requirements.txt generated by this rule should
@@ -166,7 +166,7 @@ def pip_compile(
     timeout = kwargs.pop("timeout", "short")
 
     py_test(
-        name = name + "_test",
+        name = name + ".test",
         timeout = timeout,
         # setuptools (the default python build tool) attempts to find user
         # configuration in the user's home direcotory. This seems to work fine on
@@ -180,3 +180,9 @@ def pip_compile(
         # kwargs could contain test-specific attributes like size
         **dict(attrs, **kwargs)
     )
+
+    native.alias(
+        name = "{}_test".format(name),
+        actual = ":{}.test".format(name),
+        deprecation = "Use '{}.test' instead. The '*_test' target will be removed in the next major release.".format(name),
+    )