Move min, max, clamp, minmax routines out of Experimental namespace

[ajpowelsnl]

Fixes #5168.

I propose moving the min, max, clamp and minmax routines out of the Experimental namespace, and into the Kokkos namespace.

I developed these changes using this build:

cmake \
-DKokkos_ENABLE_TESTS=ON \
-DKokkos_ENABLE_CUDA=ON \
-DKokkos_ENABLE_CUDA_LAMBDA=ON \
-DKokkos_ARCH_VOLTA70=ON \
-DKokkos_ENABLE_SERIAL=ON \
-DCMAKE_CXX_STANDARD=14 \
-DCMAKE_BUILD_TYPE=Release ..\

I ran all unit tests thusly:

ctest --output-on-failure

All tests passed.

[masterleinad]

We should rather deprecate using the functions in the Experimental namespace rather than outright removing them.
Also, you need to fix the indentation using clang-format-8.

[fnrizzi]

I agree on deprecating

[masterleinad]

The only disadvantage with this approach I see is that we don't get deprecation warnings. Of course, we followed the same approach when promoting the math functions from the Experimental namespace.

Crucial changes were made.

[fnrizzi]

if this is how the math functins were promoted, i am ok with this