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/facet-counts/exact/go.go

@@ -0,0 +1,11 @@
+package snippet
+
+
+
+func Main() {
+	res, err := client.Facet(ctx, &qdrant.FacetCounts{
+	    CollectionName: "{collection_name}",
+	    Key:            "key",
+	    Exact:          true,
+	})
+}