Replace mask_hdiff by multiplying with 0.0

[jcanton]

When naively translating a Fortran list to a full field, we constructed a mask instead of using the fact that we are actually initializing a weight with 0.0 in the masked-out cases.

Additionally: Remove program and a trivial test.

same as #1053 but for mask_hdiff

[jcanton]

cscs-ci run default

[jcanton]

cscs-ci run distributed

[github-actions]

Mandatory Tests

Please make sure you run these tests via comment before you merge!

• cscs-ci run default
• cscs-ci run distributed

Optional Tests

To run benchmarks you can use:

• cscs-ci run benchmark-bencher

To run tests and benchmarks with the DaCe backend you can use:

• cscs-ci run dace

To run test levels ignored by the default test suite (mostly simple datatest for static fields computations) you can use:

• cscs-ci run extra

For more detailed information please look at CI in the EXCLAIM universe.

[muellch]

@havogt This one is even better for a performance comparison.

• The frequency the mask is true is very very small
• The combined stencil around this one is way smaller, so differences are easier to see.

[muellch]

Same problem as before, makes code cleaner but might degrade performance.
This one should be a more obvious example since the mask is true only for few points.