Update NESO to use nektar 5.7

[oparry-ukaea]

Description

Updates for (upcoming) nektar v5.7. Aim is to keep this PR up-to-date with nektar/master until 5.7 is released.

Type of change

Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality) ~- [ ] Bug fix (non-breaking change)~ ~- [ ] API change (breaks downstream workflows and requires major semver bump)~ ~- [ ] Requires documentation updates~

Testing

Existing unit and integration tests pass.

Test Configuration:

OS: Ubuntu 22.04 Compiler: GCC 11.3.0 / OneAPI v2022.1.0 SYCL implementation: Hipsycl v0.9.2 / DPC++ v2022.1.0 MPI details: MPICH v4.0.2 Hardware: CPU (Intel Alder Lake)

Checklist:

~- [ ] I have added tests that prove my fix is effective or that my feature works~ ~- [ ] Any new dependencies are automatically built for users via cmake~ ~- [ ] I have used understandable variable names~ ~- [ ] I have run cmake-format against my changes to CMakeLists.txt~ ~- [ ] I have run black against changes to *.py~ ~- [ ] I have made corresponding changes to the documentation~

• [x] New and existing unit tests pass locally with my changes
• [x] I have run clang-format against my *.hpp and *.cpp changes
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] My changes generate no new warnings