lib.init.detect_modules(): Add function

Not all __init__.py modules are generated by python-tools.sh, some are needed early to make jw-pkg useful without generation, notably in jw.pkg.cmds.
Add detect_modules() to unify that detection, and place it into a minimal module lib.init to not increase startup time cost.
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/init.py

@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from collections.abc import MutableMapping
+    from typing import Any, Iterable
+
+def detect_modules(
+    package_name: str,
+    package_path: Iterable[str],
+    namespace: MutableMapping[str, Any],
+    prefix: str,
+    skip: set[str] | None = None,
+) -> list[str]:
+
+    import importlib
+    import pkgutil
+
+    ret: list[str] = []
+    skip = skip or set()
+
+    for _finder, module_name, _ispkg in pkgutil.iter_modules(package_path):
+        if not module_name.startswith(prefix):
+            continue
+
+        if module_name in skip:
+            continue
+
+        module = importlib.import_module(f'.{module_name}', package_name)
+        cls = getattr(module, module_name)
+
+        namespace[module_name] = cls
+        ret.append(module_name)
+
+    return ret