ci: Use GITHUB_OUTPUT envvar instead of set-output command

[arunsathiya]

save-state and set-output commands used in GitHub Actions are deprecated and GitHub recommends using environment files.

This PR updates the usage of ::set-output to "$GITHUB_OUTPUT"

Instructions for envvar usage from GitHub docs:

https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-output-parameter

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 82.10%. Comparing base (31f278f) to head (3f431bd).

:exclamation: Current head 3f431bd differs from pull request most recent head 042d6ae. Consider uploading reports for the commit 042d6ae to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #494 +/- ## ======================================= Coverage 82.10% 82.10% ======================================= Files 54 54 Lines 2191 2191 Branches 511 511 ======================================= Hits 1799 1799 Misses 329 329 Partials 63 63 ```

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