How to update Linux CI away from deprecated ubuntu 18.04 and macos 10.15?

[jhmgoossens]

The linux-ci builds produce a number of deprecation warnings, most of which are about node.js and easy to resolve.

However, the warnings about deprecated ubuntu 18.04 and macos 10.15 are a bit more tricky.

• For ubuntu, we already build 20.04, and simply adding 22.04 seems to just work.
• For macos, I tried to simply move to macos 12 but that fails during building

I'm not a mac or ubuntu user. Any comments or suggestions for macos?

[svigerske]

Dropping Ubuntu 18.04 is good.

For macOS, it seems that the specified compilers gcc-9 and gcc-10 are not found. Maybe just try gcc-11 or gcc-12?

[jhmgoossens]

Closed with #589. These were updated to ubuntu-22.04 and macos-12 with gcc-11 and gcc-12.