Fix: 'list approve_instance' pipeline id population.

[BlueLabelscotch]

This PR fixes the pipeline information displayed by the 'list approve_instance' command.
Changes:

• Populate the pipeline_id field from a different API through a fetch_fn in approve.go .
• Display the pipeline column correctly in list approve_instance.
• Add tests to verify the pipeline column is populated as expected.

[CLAassistant]

All committers have signed the CLA.

[mohitsuman]

@BlueLabelscotch can you share the screenshot/video of how the command output looks.

[BlueLabelscotch]

//
This is the correct output after the fix.

[BlueLabelscotch]

This is before the fix. Same command.