Add navier-stokes example

[yasahi-hpc]

This PR aims at adding a 3D-NS solver as an advanced example.

• Kokkos version
• Python version
• README.md

[tpadioleau]

What new features does this example explore compared to "10_HasegawaWakatani" ?

[yasahi-hpc]

What new features does this example explore compared to "10_HasegawaWakatani" ?

Not much, just more practical.
This can be a good example for distributed FFT

[tpadioleau]

Not much, just more practical.
This can be a good example for distributed FFT

I would be in favor of adding a simpler example for a distributed example.

[yasahi-hpc]

Not much, just more practical.
This can be a good example for distributed FFT

I would be in favor of adding a simpler example for a distributed example.

That is right. I have already prepared a trivial example.
This one is used to demonstrate the performance in a realistic use case.