ENH: COMP: Adding LinuxCxx20 job to Azure continuous integration.

[devbanu]

This fixes #3097 by adding a LinuxCxx20 job with the Azure continuous integration.

In the future, as ITK project itself adopts newer standards, it is easy to change this job to use C++23, etc.

This is essentially a clone of the Linux job with CMAKE_CXX_STANDARD set to 20 and CMAKE_CXX_STANDARD_REQUIRED enabled.

PR Checklist

• No API changes were made (or the changes have been approved)
• No major design changes were made (or the changes have been approved)
• Added test (or behavior not changed)
• Updated API documentation (or API not changed)
• Added license to new files (if any)
• Added Python wrapping to new files (if any) as described in ITK Software Guide Section 9.5
• Added ITK examples for all new major features (if any)

Refer to the ITK Software Guide for
further development details if necessary.

[github-actions]

Thank you for contributing a pull request! 🙏

Welcome to the ITK community! 🤗👋☀️

We are glad you are here and appreciate your contribution. Please keep in mind our community participation guidelines. 📜
More support and guidance on the contribution process can be found in our contributing guide. 📖

This is an automatic message. Allow for time for the ITK community to be able to read the pull request and comment
on it.

[seanm]

@devbanu I don't know this language/syntax, but why ubuntu-20.04? Maybe a newer Ubuntu would be wise for such a new C++?

[dzenanz]

Looks good on a glance, let's see what CI says after it finishes running.

[hjmjohnson]

Please change the vmImage to ubuntu-24.04 for more commonly found c++20 enviroinment.

[devbanu]

@hjmjohnson

Looking here:

https://learn.microsoft.com/en-us/azure/devops/pipelines/agents/hosted?view=azure-devops&tabs=yaml

there is also the option to put ubuntu-latest which currently is Ubuntu 22.04 but will soon move to Ubuntu 24.04.

What do you think ubuntu-latest (updates automatically, but maybe unexpectedly) vs ubuntu-24.04 (has to be updated manually)?

[dzenanz]

I think we decided that we prefer manual updates. They are not hard, and we can choose the time of when to do it.

Addressed

[thewtex]

What do you think ubuntu-latest (updates automatically, but maybe unexpectedly) vs ubuntu-24.04 (has to be updated manually)?

The best practice is to use explicit versioning and update so unrelated errors do not occur when latest happens to update.

[thewtex]

@devbanu thank you for the contribution! 🥇