Re evaluate golanci-lint exclusions (dupl, gofumpt, nestif)

[lburgazzoli]

Relates to #5486

This PR touches a number source files as consequence of re-enabling the nestif linter, which I think is good to have enabled as it allow to follow the happy path is left-aligned go proverb, making the code easier to understand as you should quickly be able to scan down to see the expected execution flow.

• Go’s Approach to Error Handling
• Align the happy path to the left edge
• Go Happy Path: the Unindented Line of Sight