dvc.build: move logic out of __init__ to dvc.build (#9563)

dvc/__init__.py

@@ -3,11 +3,8 @@ DVC
 ----
 Make your data science projects reproducible and shareable.
 """
-from typing import Optional
-
 import dvc.logger
-from dvc import _build
+from dvc.build import PKG  # noqa: F401
 from dvc.version import __version__, version_tuple  # noqa: F401
 
-PKG: "Optional[str]" = _build.PKG
 dvc.logger.setup()

dvc/build.py

@@ -0,0 +1,5 @@
+from typing import Optional
+
+from . import _build
+
+PKG: "Optional[str]" = _build.PKG