GitHub Actions update warnings

[Gareth Sylvester-Bradley]

These have recently started appearing in GitHub Actions output:

Node.js 12 actions are deprecated. For more information see: https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/. Please update the following actions to use Node.js 16: actions/checkout, actions/setup-python, lukka/get-cmake, lukka/run-cmake, lukka/run-cmake, lukka/run-cmake, actions/checkout

The set-output command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

I don't think the nmos-cpp scripts are using set-output directly, so it must be one of the actions that they use...

[Gareth Sylvester-Bradley]

#291 resolves all of these except the complaints about lukka/run-cmake because I didn't have time to think about starting to use CMakePresets.json that v10 brings in.