Increase SH code coverage

[joobog]

Description

This pull request adds a new test loop to tests/grib_dump.sh to ensure the grib_dump tool runs on the sh_pl_grib2.tmpl sample file if it exists. This improves test coverage for the SH accessor.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[sawom666]

We already have a test file for grib_dump -D
See
tests/grib_dump_debug.sh

Why not put this test in there?