PS-10071 [DOCS] - update Threadpool to add implementation 8.0

	new file:   docs/_static/thread-pool-diagram.png
	modified:   docs/threadpool.md

Author: patrickbirch

docs/_static/thread-pool-diagram.png

@@ -8,6 +8,8 @@ The default method, called one-thread-per-connection, creates a new thread for e
 
 MySQL supports thread pooling through the thread pool plugin, which replaces the default one-thread-per-connection model. When a statement arrives, the thread group either begins executing it immediately or queues it for later execution in a round-robin fashion. The high-priority queue consists of several thread groups, each managing client connections. Each thread group has a listener thread that listens for incoming statements from the connections assigned to the group. The thread pool exposes several system variables that can be used to configure its operation, such as thread_pool_size, thread_pool_algorithm, thread_pool_stall_limit, and others.
 
+<img src="../_static/thread-pool-diagram.png" alt="Thread pool diagram" width="600" />
+
 The thread pool plugin consists of several thread groups, each of which manages a set of client connections. As connections are established, the thread pool assigns them to thread groups using the round-robin method. This method assigns threads fairly and efficiently. Here's how it works:
 
 1. The thread pool starts with a set number of thread groups.