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/inference/openai-upsert/rust.rs

@@ -0,0 +1,27 @@
+use qdrant_client::{
+    Payload, Qdrant, QdrantError,
+    qdrant::{Document, PointStruct, UpsertPointsBuilder},
+};
+use std::collections::HashMap;
+
+pub async fn main() -> anyhow::Result<()> {
+    let client = Qdrant::from_url("<your-qdrant-url>").build()?;
+    let mut options = HashMap::new();
+    options.insert("openai-api-key".to_string(), "<YOUR_OPENAI_API_KEY>".into());
+    options.insert("dimensions".to_string(), 512.into());
+
+    client
+        .upsert_points(UpsertPointsBuilder::new("{collection_name}",
+            vec![
+                PointStruct::new(1,
+                    Document {
+                      text: "Recipe for baking chocolate chip cookies".into(),
+                      model: "openai/text-embedding-3-large".into(),
+                      options,
+                      },
+                    Payload::default())
+                ]).wait(true))
+            .await?;
+
+    Ok(())
+}