feat: routes for adding/linking new memory blocks to agents + unlinking blocks from agents

[cpacker]

• Adds two new REST routes for linking and unlinking blocks from an agents memory
  • @router.post("/{agent_id}/memory/block", response_model=Memory, operation_id="add_agent_memory_block")
  • @router.delete("/{agent_id}/memory/block/{block_label}", response_model=Memory, operation_id="remove_agent_memory_block")
• Adds a third REST route for updating the label of a current block
  • @router.patch("/{agent_id}/memory/label", response_model=Memory, operation_id="update_agent_memory_label")