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/retrieve-points/simple/go.go

@@ -0,0 +1,21 @@
+package snippet
+
+import (
+	"context"
+
+	"github.com/qdrant/go-client/qdrant"
+)
+
+func Main() {
+	client, err := qdrant.NewClient(&qdrant.Config{
+		Host: "localhost",
+		Port: 6334,
+	})
+
+	client.Get(context.Background(), &qdrant.GetPoints{
+		CollectionName: "{collection_name}",
+		Ids: []*qdrant.PointId{
+			qdrant.NewIDNum(0), qdrant.NewIDNum(3), qdrant.NewIDNum(100),
+		},
+	})
+}