refactor: separate tech specific code

Make the codebase more PDK-agnostic by moving tech-specific code to `tech.py` and tech specific files (e.g. def files, tile_sizes.yaml) to `tech/<pdkname>` subdirectory.

tech/sky130A/create_cell_defs.py

@@ -0,0 +1,40 @@
+import glob
+import json
+import os
+from typing import Dict, List, Optional, TypedDict
+
+
+class Port(TypedDict):
+    kind: str
+    name: str
+    direction: str
+    description: str
+
+
+class Sky130Cell(TypedDict):
+    description: str
+    file_prefix: str
+    library: str
+    name: str
+    parameters: List[str]
+    ports: List[Port]
+    type: str
+    verilog_name: str
+    equation: Optional[str]
+
+
+def create_cell_defs():
+    json_files = glob.glob("sky130_fd_sc_hd/latest/cells/*/definition.json")
+    definitions: Dict[str, Sky130Cell] = {}
+    for json_file in json_files:
+        with open(json_file) as fh:
+            definition: Sky130Cell = json.load(fh)
+            definitions[definition["name"]] = definition
+
+    script_dir = os.path.dirname(os.path.realpath(__file__))
+    with open(f"{script_dir}/cells.json", "w") as fh:
+        json.dump(definitions, fh)
+
+
+if __name__ == "__main__":
+    create_cell_defs()