Go: improve post-update node tests

[owen-mc]

We should be testing post-update nodes for method calls. It turns out that we don't generate post-update nodes for receivers of method calls when they are made indirectly, via a variable. (The code looks like it tries to, but actually it will never work.) It won't always be possible to find the receiver, but when it is we probably ought to. But that is future work.

[Copilot]

Pull Request Overview

This PR improves testing for post-update nodes in Go data flow analysis by expanding test coverage to include method calls. The change reveals that post-update nodes are not generated for receivers of indirect method calls (calls made through variables), which is noted as future work to address.

Key changes:

• Enhanced the test query to display both post-update nodes and their corresponding pre-update nodes
• Added test cases for direct and indirect method calls to verify post-update node generation

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
test.ql	Modified query to output pre-update nodes alongside post-update nodes for better test visibility
test.go	Added method definitions and test cases for direct/indirect method calls to expand test coverage
test.expected	Updated expected output to reflect the enhanced query results and new test cases