Handle Key Events in CPCIE_PICMG

Design Event Handlers for CPCIE_PICMG

1. Planning Key Events for UI Control Modification
When designing modifications to default behaviors of UI controls in CPCIE_PICMG, it's crucial to account for both mouse and keyboard access to functions. The default TreeView control supports several key events:

- Up/Down Arrow Keys: Move the cursor, changing the currently selected node.
- Left/Right Arrow Keys: In addition to changing the selected node, these keys can expand/collapse the node and create nodes.
- Enter Key: Also allows expanding/collapsing and node creation.

Additional Key Events:
- Insert Key: Inserts a new node below the current one; pressing Ctrl + Insert adds a root node. After insertion, the control enters edit mode, allowing the user to press Enter to exit edit mode. This also highlights the parent node, letting the user insert additional sibling nodes easily.
- Delete Key: Deletes the selected node, removing any child nodes.
- Space Key: Puts the selected node into edit mode.

2. Implementing Event Handlers
The KeyDown event handler in the TreeView control processes all key-related editing actions. A Select Case block identifies which key is pressed, with each Case corresponding to a specific action:
- For Space, the StartLabelEdit method is called to enable edit mode.
- For Delete, the selected node is removed with TreeView.Nodes.Remove.
- For Insert, the code snippet below adds a new child node under the selected node and initiates edit mode.

These controls improve navigation and editing efficiency, enhancing user experience for keyboard navigation and editing within the control.