Make OpenMP tests be explicit w.r.t. schedule clause

[rhornung67]

Is your feature request related to a problem? Please describe.

Some compilers, such as Intel, do not choose static scheduling by default in their OpenMP implementation. This can cause some of our tests to fail.

Most other compilers do choose static scheduling by default.

Describe the solution you'd like

Make all RAJA tests, examples, exercises, etc. explicitly set the OpenMP schedule in their execution policies.

Describe alternatives you've considered

A clear and concise description of any alternative solutions or features you've considered.

Additional context

The OpenMP standard does not state what the default scheduling policy should be when a user does not specify. It is left to the implementation to choose.