Highlight definition and control block structures

[ro-gun]

Motivation

Closes #2494

Implementation

If the cursor is on a definition or control node, both the start and end of the node will be highlighted.

Automated Tests

Amended existing test case.

Manual Tests

Place the cursor on one of the definition or control nodes.

Screencast from 25-10-24 08:44:06 AM IST.webm