HIP: Increase to C++17

[ax3l]

Summary

Bump HIP requirements to C++17 or newer (like DPC++).
At the moment, we only test against AMD's clang++/hipcc, which supports C++17 anyway.

Additional background

• Add more warnings to CI and fix warnings #2104 (comment)
• -x hip Should have same C++ std as -x c++ ROCm/hip#2278

Checklist

The proposed changes:

• fix a bug or incorrect behavior in AMReX
• add new capabilities to AMReX
• changes answers in the test suite to more than roundoff level
• are likely to significantly affect the results of downstream AMReX users
• are described in the proposed changes to the AMReX documentation, if appropriate

[ax3l]

As of comment #2104 (comment) we might not want to do this yet.

Although it simplifies #2031 due to the linked bug above (or we wait for ROCm 4.4 to carve out this issue or fixate the build to C+14 only in the meantime).