Generate multiple code snippets from a single source file (#2146)

* Support generating multiple snippets from one source file

* Convert Python code snippets from one source file

* Add code snippets for C#, Go, Java, Rust and TS

* Make intro less Python-oriented

* Add client installation instructions for all languages

* Cleanup python code

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Co-authored-by: xzfc <xzfcpw@gmail.com>

qdrant-landing/content/documentation/headless/snippets/install-client/csharp.md

@@ -0,0 +1,3 @@
+```csharp
+Qdrant.Client
+```

qdrant-landing/content/documentation/headless/snippets/install-client/go.md

@@ -0,0 +1,3 @@
+```go
+github.com/qdrant/go-client
+```

qdrant-landing/content/documentation/headless/snippets/install-client/java.md

@@ -0,0 +1,3 @@
+```java
+io.qdrant:client
+```

qdrant-landing/content/documentation/headless/snippets/install-client/python.md

@@ -0,0 +1,3 @@
+```python
+qdrant-client
+```

qdrant-landing/content/documentation/headless/snippets/install-client/rust.md

@@ -0,0 +1,3 @@
+```rust
+qdrant-client
+```

qdrant-landing/content/documentation/headless/snippets/install-client/typescript.md

@@ -0,0 +1,3 @@
+```typescript
+qdrant/js-client-rest
+```