improve the module importer's robustness

This fixes the following issues:

- The old code inserted the "current working dir" into the module search paths, which has no correlation to the OneTrainer directory if the user executes the scripts with another active working directory. Now we use the actual OneTrainer directory regardless of its location, by leveraging the excellent Path library.

- The previous code inserted our path *last*, which meant that every import prioritized all other paths before looking in OneTrainer. This could lead to shadowing issues if a user has a system where a path contains another module named "modules", such as their own homemade project. We now insert ourselves at the top, as the highest priority.

- `scripts/install_zluda.py` was duplicating the efforts of importing modules. It clearly did that to avoid trying to load ZLUDA before it has been installed, but that's better handled by a loader flag instead.

- `scripts/sample.py` was permanently broken, since it attempted to import a module before fixing the import path.

scripts/install_zluda.py

@@ -1,7 +1,8 @@
-import os
-import sys
+from util.import_util import script_imports
+
+script_imports(allow_zluda=False)
 
-sys.path.append(os.getcwd())
+import sys
 
 from modules.zluda import ZLUDAInstaller
 

scripts/sample.py

@@ -1,5 +1,3 @@
-from modules.util.ModelNames import ModelNames
-
 from util.import_util import script_imports
 
 script_imports()
@@ -9,6 +7,7 @@
 from modules.util.config.SampleConfig import SampleConfig
 from modules.util.enum.ImageFormat import ImageFormat
 from modules.util.enum.TrainingMethod import TrainingMethod
+from modules.util.ModelNames import ModelNames
 from modules.util.torch_util import default_device
 
 

scripts/util/import_util.py

@@ -1,16 +1,20 @@
-def script_imports():
+def script_imports(allow_zluda: bool = True):
     import logging
     import os
     import sys
+    from pathlib import Path
 
-    # filter out the triton warning on startup
+    # Filter out the Triton warning on startup.
     logging \
         .getLogger("xformers") \
         .addFilter(lambda record: 'A matching Triton is not available' not in record.getMessage())
 
-    sys.path.append(os.getcwd())
+    # Insert ourselves as the highest-priority library path, so our modules are
+    # always found without any risk of being shadowed by another import path.
+    onetrainer_lib_path = Path(__file__).absolute().parent.parent.parent
+    sys.path.insert(0, str(onetrainer_lib_path))
 
-    if sys.platform.startswith('win'):
+    if allow_zluda and sys.platform.startswith('win'):
         from modules.zluda import ZLUDAInstaller
 
         zluda_path = ZLUDAInstaller.get_path()