Automated snippet conversion by scripts

These changes are purely mechanical to differentiate them from manual
fixes/adjustments made in the next commit.
This results in broken code as some snippets contain errors.

Made in four steps:
1. Run ./migrate-snippet.py that converts `.md` files to code files
   and perhaps adds missing lines under `// @hide` comments.
2. Sort Java imports.
3. Remove old `.md` files.
4. Run ./generate.md to produce `*/generated/*.md` files.

qdrant-landing/content/documentation/headless/snippets/fastembed/bm25/create-collection/generated/python.md

@@ -7,4 +7,4 @@ client.create_collection(
         )
     }
 )
-```
+```

qdrant-landing/content/documentation/headless/snippets/fastembed/bm25/create-collection/python.py

@@ -0,0 +1,12 @@
+from qdrant_client import QdrantClient, models  # @hide
+
+client = QdrantClient(url="http://localhost:6333")  # @hide
+
+client.create_collection(
+    collection_name="{bm25_collection_name}",
+    sparse_vectors_config={
+        "bm25": models.SparseVectorParams(
+            modifier=models.Modifier.IDF
+        )
+    }
+)