[WIP][core] C++20 upgrade

[dayshah]

Why are these changes needed?

Upgrading to C++20.

The main code changes required are around the new char8 compatibility https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1423r2.html

and the deprecation of implicit capture of this via [=] for lambdas https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0806r2.html

Related issue number

Checks

• [ ] I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• [ ] I've run scripts/format.sh to lint the changes in this PR.
• [ ] I've included any doc changes needed for https://docs.ray.io/en/master/.
  • [ ] I've added any new APIs to the API Reference. For example, if I added a method in Tune, I've added it in doc/source/tune/api/ under the corresponding .rst file.
• [ ] I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • [ ] Unit tests
  • [ ] Release tests
  • [ ] This PR is not tested :(

[dentiny]

Upgrade C++20 also requires standard library upgrade at the same time, otherwise, if we're running on an old system which doesn't have, say, <format>, we cannot enjoy all the benefits; wondering how do you plan to deal with it?

[dentiny]

Curious do we plan to merge this PR? :eyes:

[dayshah]

Curious do we plan to merge this PR? :eyes:

i think there were a couple issues with it, will look at fixing this weekend

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This pull request has been automatically marked as stale because it has not had any activity for 14 days. It will be closed in another 14 days if no further activity occurs. Thank you for your contributions.

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[github-actions[bot]]

This pull request has been automatically marked as stale because it has not had any activity for 14 days. It will be closed in another 14 days if no further activity occurs. Thank you for your contributions.

You can always ask for help on our discussion forum or Ray's public slack channel.

If you'd like to keep this open, just leave any comment, and the stale label will be removed.

[github-actions[bot]]

This pull request has been automatically marked as stale because it has not had any activity for 14 days. It will be closed in another 14 days if no further activity occurs. Thank you for your contributions.

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If you'd like to keep this open, just leave any comment, and the stale label will be removed.